Triggers: Difference between revisions

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:; No implicit context: There is no implicit context for the trigger script, as there is, for instance, in a JavaScript field. Instead, there are global functions, such as lib() and entry() that must be used to set up context for the script.
:; No implicit context: There is no implicit context for the trigger script, as there is, for instance, in a JavaScript field. Instead, there are global functions, such as lib() and entry() that must be used to set up context for the script.
:; Entry objects are clones: The Entry object associated with the Event (the one that entry() gives you) is a clone of the actual entry object. If changes are made to this object, they will be saved if the script returns normally. However, if the script calls cancel(), this clone will be discarded upon return from the script, along with any changes that have been made.
:; Entry objects are clones: The Entry object associated with the Event (the one that entry() gives you) is a clone of the actual entry object. If changes are made to this object, they will be saved if the script returns normally. However, if the script calls cancel(), this clone will be discarded upon return from the script, along with any changes that have been made.
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<br/>
== Libraries and Entries ==
=== ''Library'' Global Functions ===
==== entry() ====
: Get the Entry object of the Event. For example, if the script is triggered by an Update Entry event, this function will return the entry being updated.
: This Entry object is a clone of the actual Entry object. If the entry is saved, this object will become the actual one, but if cancel() is called, this entry clone, along with any changes the script may have performed, will be discarded.
: This function is available to all Events and Phases, with the exception of '''Creating an entry''' &gt; '''Opening an Entry Edit card'''; for this action, use the function ''entryDefault()''.
:; Result: [[#Object Entry|'''''Entry''''' object]] &mdash; the current entry
==== entryDefault() ====
: Get the Entry object containing the default field values for the entry not yet created. This feature is available specifically and only for the Event '''Creating an entry''' & Phase '''Opening an Entry Edit card'''.
:; Result: [[#Object DefaultEntry|'''''DefaultEntry''''' object]]
==== lib() ====
: Get the library of the triggering event
:; Result: [[#Object Library|'''''Library''''' object]] &mdash; the current library
==== libByName(name) ====
: Find the library by name. Permission to use the library is required, based on security settings.
:; Argument: The name of the library to find
:; Result: [[#Object Library|'''''Library''''' object]] &mdash; the library identified by the argument ''name'', if found. Otherwise ''null''.
<br/>
=== Object ''Library'' ===
This object provides access to library entries. You can work with the current library &mdash; the ''lib()'' &mdash; or any other library in the database &mdash; ''libByName()''. This function provides the ability to update existing entries and create new ones.
==== ''Library'' Methods ====
===== entries() =====
: Get all the entries of the library
:; Result: Array object containing entries, sorted by the time of their creation, from newest to oldest
===== find(query) =====
: Search field values within entries in the library matching the given query. This search is similar to searching via Memento's user interface.
:; Argument: '''query''' &mdash; the search string
:; Result: Array object containing matching entries. Entries are sorted by the time of their creation, from newest to oldest.
===== findByKey(name) =====
: Search all entries by the Entry Name. The library must be set for unique Entry Names.
:; Argument: '''name''' &mdash; the Entry Name field value
:; Result: [[#Object Entry|'''''Entry''''' object]], if found. Otherwise, ''null''.
===== create(values) =====
: Create a new entry in the library
:; Argument: '''values''' &mdash; [https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Object '''''Object'''''] containing the field values
:; Result: [[#Object entry|'''''Entry''''' object]] &mdash; the new entry in the library
===== show() =====
: Display the library
==== ''Library'' Properties ====
: '''title''' &mdash; The name of the library
<br/>
=== Object ''Entry'' ===
This object holds an entry of the current library, allowing the setting of field values
==== ''Entry'' Methods ====
===== set(name, value) =====
: Set the value of the named field. Calling this method results in immediate writing of the value to the library.
:'''Note:''' In the case where the field to be set is a Link To Entry field, the second argument should be the entry name of the entry to link to. If there are, in that library, multiple fields set as Entry Name, the entry name for the set() method is formed by separating the value of those fields by a comma (,) &mdash; not a comma and a space, but only a comma.
:; Arguments
:: '''name''' &mdash; name of the field
:: '''value''' &mdash; the value of the field
===== field(name) =====
: Get the value of the named field
:; Argument: '''name''' &mdash; name of the field
:; Result: The value of the field. The type of the result depends on the type of the field.
::{{FieldTypeReturnValues}}
===== show() =====
: Display the entry
==== ''Entry'' Properties ====
: '''name''' &mdash; entry name
: '''title''' &mdash; entry name
: '''description''' &mdash; entry description
: '''favorites''' &mdash; true, if the entry is in Favorites
: '''deleted''' &mdash; true, if the record is deleted (it is in the Recycle Bin)
<br/>
=== Object ''DefaultEntry'' ===
Template with default values for a new entry. This feature is available specifically and only for the Event '''Creating an entry''' & Phase '''Opening an Entry Edit card'''.
==== ''DefaultEntry'' Methods ====
===== set(name, value) =====
: Set the value of the field
:; Arguments
:: '''name''' &mdash; the name of the field
:: '''value''' &mdash; the value of the field
<br/>
=== Libraries Examples ===
See '''[[Trigger Examples#Libraries Examples]]'''.
<br/>
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<br/>
<br/>

Revision as of 07:22, 1 March 2017

« Page as of 2017-01-24, editions Mobile 4.2.1, Desktop 1.0.8 »

A Trigger is a script that defines the processing of an entry whenever a particular kind of event takes place. Trigger scripts are written in JavaScript. When a trigger script is executed, it may perform actions like changing an existing entry, creating a new entry, executing an HTTP request, creating a file, performing data validation, etc.


Definitions

We define the following terms:

Event type
One of the following:
  • Creating an entry
  • Updating an entry
  • Deleting an entry
  • Opening an Entry Edit card
  • Adding an entry to Favorites
  • Removing an entry from Favorites
Phase of an Event
One of a predefined set of moments during entry processing for each Event type during which the user can intervene via a trigger script. See the table of events and phases below.
The Event type and the Phase determine the trigger script(s) to be run.
Trigger or Trigger Script
A script that may be defined to run when an event occurs for an entry
The trigger (Event type & Phase) and the corresponding trigger script are one-to-one.
When referring specifically to the script, it is called the trigger script. When referring to the Event type & Phase and its listing in the trigger list, it is referred to merely as a trigger.

Mode of script execution

The phase in which the trigger is activated defines its mode of execution — synchronous or asynchronous.

Synchronous script execution mode
Memento suspends user interaction and then executes the script. In the case of Before... phases, there is an impending operation that will take place unless the script forestalls it by calling cancel().
Time-consuming operations are not recommended in this mode.
Asynchronous script execution mode
The script runs in the background; user interaction is not suspended. Usually, asynchronous scripts are used in the last phases of the action, after any save or other operation is initiated.


Events & Phases

These are the defined Event types, Phases, and their corresponding modes of execution.

THE DEFINED EVENT TYPES & THEIR PHASES
Event type Phase Execution mode
Creating an entry Opening an Entry Edit card synchronous
Before saving the entry synchronous
After saving the entry asynchronous
Updating an entry Opening an Entry Edit card synchronous
Before saving the entry synchronous
After saving the entry asynchronous
Deleting an entry Before deleting the entry synchronous
After deleting the entry asynchronous
Opening an Entry View card Before window display synchronous
After window display asynchronous
Adding an entry to Favorites Before the operation synchronous
After the operation asynchronous
Removing an entry from Favorites Before the operation synchronous
After the operation asynchronous

Creating an entry

This event starts when a user has requested that a new entry be added to the library, normally by pressing the + button on the Entries List screen. It ends after the entry is saved to storage — or else not, depending on the processing of the entry.

Phases

This event has three phases. In sequence:

1. Opening an Entry Edit card (synchronous)
The script will be called once the Entry Edit card is open and before any data is displayed.
Initial field values (defaults) may be set.
2. Before saving the entry (synchronous)
The script will be called after the user has pressed the Checkmark icon and before the entry has been saved to storage.
The entered data may be validated; if validation fails, the save may be forestalled and control sent back to the Entry Edit card so the user may fix the errors.
Once the data is validated, this phase is an opportunity for many other functions to be performed to get data to add to the entry to be saved.
3. After saving the entry (asynchronous)
The script will be called once the save of the entry has been initiated and will continue in parallel with final processing of the new entry.
If you want to do something whenever a new entry is added, but not before the data is saved, this is the place to do it.

Updating an entry

This event starts when a user has requested that an existing entry be edited (updated) within the library, normally by pressing the Pencil button on the Entry View card. It ends after the entry is resaved to storage — or else not, depending on the processing of the entry.

Phases

This event has three phases. In sequence:

1. Opening an Entry Edit card (synchronous)
The script will be called once the Entry Edit card is open and before any data is displayed.
2. Before saving the entry (synchronous)
The script will be called after the user has pressed the Checkmark icon and before the entry has been saved to storage.
The entered data may be validated; if validation fails, the save may be forestalled and control sent back to the Entry Edit card so the user may fix the errors.
Once the data is validated, this phase is an opportunity for many other functions to be performed to get data to add to the entry to be saved.
The script could be used to update some entry data based on other entry data, to keep it all coordinated.
3. After saving the entry (asynchronous)
The script will be called once the save of the entry has been initiated and will continue in parallel with final processing of the new entry.
If you want to do something whenever an existing entry is updated, but not before the data is saved, this is the place to do it.

Deleting an entry

This event starts when a user has requested that an existing entry be deleted (actually, moved to the library's Recycle Bin) within the library, normally by pressing the Trash Can button on the Entry View card. It ends after the entry is moved to the Recycle Bin — or else not, depending on the processing of the entry.

Phases

This event has two phases. In sequence:

1. Before deleting the entry (synchronous)
This script will be called after the user has requested the deletion of the entry and pressed Yes on the "Do you really want to?" card, but before taking the action.
Since the user has at this point already confirmed that he or she really wants to delete that entry, what else needs to be done before doing the delete? And what would cause the delete to need to be forestalled? If the delete is to be forestalled, the script could call cancel() and inform the user as to why via message(), and let the user reconsider what to do.
Mainly, help the user reconfirm that the deletion should take place, and if not, call cancel() and inform the user (via message()).
2. After deleting the entry (asynchronous)
This script will be called after the delete operation is initiated and will continue as that operation takes place.
Anything you want to do whenever an entry is deleted should be done in this script.

Opening an Entry View card

This event starts when the user has selected an entry for view and ends after the entry had been displayed.

Phases

This event has two phases. In sequence:

1. Before window display (synchronous)
This script will be called before the entry is displayed. This provides the opportunity to alter or augment the data before it is seen by the user.
2. After window display (asynchronous)
This script will be called after the data display had been initiated, providing the opportunity to perform an action each time an entry had been viewed, such as logging or timestamping.

Adding an entry to Favorites

This event starts when the user has pressed an empty Star icon to make the current entry a Favorite and ends once it has been made a Favorite.

Phases

This event has two phases. In sequence:

1. Before the operation (synchronous)
This script is run just before the entry is made a Favorite.
Data validation could be done; perhaps only certain entries are allowed to be Favorites.
2. After the operation (asynchronous)
This script is called after the entry has been made a Favorite.
This action could be logged, for instance, or it could trigger an action on some other app.

Removing an entry from Favorites

This event starts when the user has pressed a filled Star icon to remove the current entry from Favorites and ends once it has been removed.

Phases

This event has two phases. In sequence:

1. Before the operation (synchronous)
This script is run just before the entry is removed from Favorites.
Confirmation of the user's intent could go here.
2. After the operation (asynchronous)
This script is called after the entry has been removed from Favorites.
This action could be logged, for instance, or it could trigger an action on some other app.


Security

Since the scripts have access to more actions than a user does, they require additional permissions.

The user must define these permissions manually for each library.

To open a card to set permissions for scripts, open the library triggers list and click the Shield icon on the toolbar. Permissions must be set separately on each device. Permissions are not synchronized between devices.

Permissions for scripts

Library permission
determines which other libraries can be affected by the script. You can grant access to all libraries or select only certain libraries. This authorization is required for the libByName() function.
Read permission
grants the script read access to a file
Write permission
grants the script write access to a file
Network
grants to the script the right to execute HTTP requests


Creating a trigger

Each library can have a number of triggers; multiple triggers may exist for each Event type and Phase. To see the list of triggers, open the library, open the menu, and then select Triggers.

To create a trigger, press the 3-dot icon in the upper-right corner of the screen to open the Action Menu; then press Triggers to open the list of existing triggers; then click +. You must then identify the Event type & Phase and write a trigger script that performs the necessary actions.

Writing a Trigger Script

Trigger scripts are JavaScripts. See links to JavaScript documentation below.

Event & Phase
Make sure to understand the Event & Phase you are scripting. This will dictate a number of things, such as whether data is present already or not, whether cancel() makes sense or not, whether the user is waiting for script execution or not, and so on.
Globals get you started
Note the global functions in the sections below; they generally get you started by providing needed information.
Inform the user
Keep the user informed. For instance, if a script is running in a synchronous phase, then a call to cancel() may make sense, but the user won't know what happened and what to do next unless you provide that information, probably via message().
Debug your script
Of course, you can put calls to message("Your message") to help to test your script. To further assist, the log("Your message") global function can be used to send messages to a log without bothering the user about it. By default, the log is directed to the Android developer console; to have it directed instead to a file, go to Memento Settings under Debug and turn on Triggers Logs. You can set the location for the file, but by default, it will be in memento/logs. Both messages from calls to log() and system log messages, including JavaScript exceptions, go into the log.
Permissions
Certain functions require special permissions; read above about that. One such function is libByName(). Others include the file access and HTTP functions.
No return
As of release 4.0.0 of the mobile edition, the script is executed as a top-level script and not as a called function; therefore, for instance, the return statement is not appropriate in a trigger script.

Things to know while writing a trigger script

No implicit context
There is no implicit context for the trigger script, as there is, for instance, in a JavaScript field. Instead, there are global functions, such as lib() and entry() that must be used to set up context for the script.
Entry objects are clones
The Entry object associated with the Event (the one that entry() gives you) is a clone of the actual entry object. If changes are made to this object, they will be saved if the script returns normally. However, if the script calls cancel(), this clone will be discarded upon return from the script, along with any changes that have been made.


Working with files

With scripts, you can read or write files located in the device's internal memory or on the SD card. All file operations are performed by the File object, which is obtained via a global function called file().

To work with the files, the library should have read/write file access.

File Global Functions

file(name)

Open a file for read or write operations. If the file with the specified name does not exist yet, it will be created.

Argument
name — The name and the full path to the file. For example, if the file is located on the SD card, the path should be something like /sdcard/example.txt.
Result
File object


Object File

This object is returned by the global function file() and provides access to the requested file. After reading or writing, the file should be closed using the method close().

File Methods

readAll()
Reads all lines of the file, and then closes the file
Returns
Array containing the lines of the file
readLine()
Reads the next line from the file stream
Returns
The line
readLines()
Reads the remaining lines from the file stream
Returns
Array containing the remaining lines of the file
readChar()
Reads the next character from the file stream
Returns
The character
write(text)
Write string(s). Take a variable number of arguments, converts each argument to a string, and writes that string to the file stream.
writeLine(text)
Write strings and a newline to the file stream
close()
Close the file. It can subsequently be reopened.

File Properties

exists
true — if and only if the file exists; false otherwise
length
The length, in bytes, of the file, or 0L if the file does not exist.
getLineNumber
Get the current line number
Returns
The line number, or position, in the file


Files Examples

See Trigger Examples#Files Examples.



Processing an HTTP request

Scripts can send HTTP requests to Web services through their APIs. Processing for HTTP requests allows integration between Memento and the system. All file operations use the Http object, which works through global function http().

HTTP requests must fulfill two requirements:

  1. Script execution must be asynchronous, so HTTP requests go in the last Phase of an Event.
  2. The library should have the permission Network.


Object Http

Interface for processing HTTP requests

Http Methods

get(url)
Execute HTTP get request
Argument
url — HTTP address, starting with http or https
Result
HttpResult — Object containing the result of the execution of the HTTP request


Object HttpResult

Result of the execution of the HTTP request

HttpResult Properties

code — HTTP code of the response, if the request is successful (usually 200).
body — The response in text form


Http Examples

See Trigger Examples#Http Examples.



Interaction with the System

System Global Functions

message(text)

Shows the user a brief notification
Argument
text — Text of the notification

cancel()

Stop the system operation that caused the event. Many triggers can be a result of an entry manipulation (create, update, delete, etc). The cancel() function can be used during the phases that precede the system operation. For example, this function can be used during data validation before the entry is saved.

system()

Obtain information about the system
Result
System object

log(text)

Write a line to the log file
Argument
text — text to be written to the log

guid()

Generates random text identifier
Result
Random string identifier

intent(action)

Create an information exchange object — Intent. This function can send a request for action to another application.
This function is available only on Android.
Argument
action — Line that defines standard action (eg, view, pick)
Result
Intent object — Information exchange object
After the object is received, the data will be added to it, and then sent via send().
Android has many built-in actions. A list of these actions can be found here.


Object System

This object contains information about the system.

System Properties

os — Name of the operating system executing the script


Object Intent

Information exchange object. This object is created by using the global function intent().

Intent Methods

data(uri)
Define URI to reference the data
Argument
uri — URI referencing data to which the action will be applied. It can be contact ID, path to the file, phone number, etc.
mimeType(mime)
Define MIME type of the data
Argument
mime — MIME type of the data on which the operation will be performed
extra(key, value)
Define additional data as key-value pairs, as necessary for execution of the required action. Similar to how URI data can be required for certain actions, other actions may require extra data in this format.
Arguments
key and value
extraLong(key, value)
Define additional data as key-value pairs, where data type needs to be Long
Arguments
key and value
send()
Send a message


System Examples

See Trigger Examples#System Examples.



Built-in objects for certain Memento field types

Object JSContact

This object contains the information stored within a Contact field and provides properties and methods for use in accessing and manipulating this information.

When an Entry object's field() method is called, if the Memento field type is Contact, a JSContact object is returned.

If the Contact field contains multiple contacts, use hasNext and next to retrieve them.

JSContact Methods

show()
Opens the Contacts app for this contact
call()
If the device is a phone, calls the primary phone number of this contact
sendSMS(message)
If the device is a phone, sends the provided message (text string) as an SMS message to the primary phone number of this contact
sendEmail(subject, message)
Sends an email message to the primary email address of this contact, with subject subject and message message (text string)

JSContact Properties

fullName
The full name of this contact
phone
The primary phone number of this contact
email
The primary email address of this contact
hasNext
Returns TRUE if there is a next JSContact object, otherwise FALSE
next
Returns the next JSContact object, if there is one.


Object JSGeolocation

This object contains the information stored within a Location field and provides properties and methods for use in accessing and manipulating this information.

When an Entry object's field() method is called, if the Memento field type is Location, a JSGeolocation object is returned.

If the Location field contains multiple locations, use hasNext and next to retrieve them.

JSGeolocation Properties

lat
Latitude, as a Real
lng
Longitude, as a Real
address
Address for this Location
hasNext
Returns TRUE if there is a next JSGeolocation object, otherwise FALSE
next
Returns the next JSGeolocation object, if there is one.




Built-in Objects Examples

See Trigger Examples#Built-in Objects Examples.



See also

Examples of trigger scripts Trigger Examples




JavaScript links

W3Schools
JavaScript Tutorial A pleasant, fairly complete, and useful tutorial on JavaScript
Best on a computer or tablet in landscape. On a phone or tablet in portrait, scroll to the bottom for navigation.
Mozilla Developer Network
JavaScript Guide Shows you how to use JavaScript, gives an overview of the language, and presents its capabilities & features
JavaScript Reference The entire JavaScript language described in detail
Introduction to JavaScript Introduces JavaScript and discusses some of its fundamental concepts
JavaScript Tutorial A re-introduction. JavaScript is often derided as being a toy, but beneath its simplicity, powerful language features await.
JavaScript 1.7 The JavaScript release upon which Memento is currently based
About JavaScript Jumping off point in learning about JavaScript