Command (core)
@ckeditor/ckeditor5-core/src/command
Base class for the CKEditor commands.
Commands are the main way to manipulate the editor contents and state. They are mostly used by UI elements (or by other commands) to make changes in the model. Commands are available in every part of the code that has access to the editor instance.
Instances of registered commands can be retrieved from editor.commands
.
The easiest way to execute a command is through editor.execute()
.
By default, commands are disabled when the editor is in the read-only mode
but commands with the affectsData
flag set to false
will not be disabled.
Filtering
Properties
-
affectsData : boolean
module:core/command~Command#affectsData
A flag indicating whether a command execution changes the editor data or not.
Commands with
affectsData
set tofalse
will not be automatically disabled in the read-only mode and other editor modes with restricted user write permissions.Note: You do not have to set it for your every command. It is
true
by default.Parameters
affectsData : boolean
-
The editor on which this command will be used.
-
Flag indicating whether a command is enabled or disabled. A disabled command will do nothing when executed.
A given command class should control this value by overriding the
refresh()
method.It is possible to disable a command "from outside" using
forceDisabled
method. -
The value of the command. A given command class should define what it represents for it.
For example, the
'bold'
command's value indicates whether the selection starts in a bolded text. And the value of the'link'
command may be an object with link details.It is possible for a command to have no value (e.g. for stateless actions such as
'uploadImage'
).A given command class should control this value by overriding the
refresh()
method. -
protected
_isEnabledBasedOnSelection : boolean
module:core/command~Command#_isEnabledBasedOnSelection
A flag indicating whether a command's
isEnabled
state should be changed depending on where the document selection is placed.By default, it is set to
true
. If the document selection is placed in a non-editable place (such as non-editable root), the command becomes disabled.The flag should be changed to
false
in a concrete command's constructor if the command should not change itsisEnabled
accordingly to the document selection. -
A flag indicating whether a command execution changes the editor data or not.
Related:
-
Holds identifiers for
forceDisabled
mechanism.
Methods
-
constructor( editor )
module:core/command~Command#constructor
Creates a new
Command
instance.Parameters
editor : Editor
The editor on which this command will be used.
-
Binds observable properties to other objects implementing the
Observable
interface.Read more in the dedicated guide covering the topic of property bindings with some additional examples.
Consider two objects: a
button
and an associatedcommand
(bothObservable
).A simple property binding could be as follows:
button.bind( 'isEnabled' ).to( command, 'isEnabled' );
or even shorter:
button.bind( 'isEnabled' ).to( command );
which works in the following way:
button.isEnabled
instantly equalscommand.isEnabled
,- whenever
command.isEnabled
changes,button.isEnabled
will immediately reflect its value.
Note: To release the binding, use
unbind
.You can also "rename" the property in the binding by specifying the new name in the
to()
chain:button.bind( 'isEnabled' ).to( command, 'isWorking' );
It is possible to bind more than one property at a time to shorten the code:
button.bind( 'isEnabled', 'value' ).to( command );
which corresponds to:
button.bind( 'isEnabled' ).to( command ); button.bind( 'value' ).to( command );
The binding can include more than one observable, combining multiple data sources in a custom callback:
button.bind( 'isEnabled' ).to( command, 'isEnabled', ui, 'isVisible', ( isCommandEnabled, isUIVisible ) => isCommandEnabled && isUIVisible );
Using a custom callback allows processing the value before passing it to the target property:
button.bind( 'isEnabled' ).to( command, 'value', value => value === 'heading1' );
It is also possible to bind to the same property in an array of observables. To bind a
button
to multiple commands (alsoObservables
) so that each and every one of them must be enabled for the button to become enabled, use the following code:button.bind( 'isEnabled' ).toMany( [ commandA, commandB, commandC ], 'isEnabled', ( isAEnabled, isBEnabled, isCEnabled ) => isAEnabled && isBEnabled && isCEnabled );
Parameters
bindProperties : Array<'off' | 'on' | 'once' | 'listenTo' | 'stopListening' | 'fire' | 'delegate' | 'stopDelegating' | 'set' | 'bind' | 'unbind' | 'decorate' | 'destroy' | 'value' | 'execute' | 'isEnabled' | 'affectsData' | 'refresh' | 'editor' | 'forceDisabled' | 'clearForceDisabled'>
Observable properties that will be bound to other observable(s).
Returns
MultiBindChain
The bind chain with the
to()
andtoMany()
methods.
-
inherited
bind( bindProperty1, bindProperty2 ) → DualBindChain<K1, Command[ K1 ], K2, Command[ K2 ]>
module:core/command~Command#bind:DUAL_BIND
Binds observable properties to other objects implementing the
Observable
interface.Read more in the dedicated guide covering the topic of property bindings with some additional examples.
Consider two objects: a
button
and an associatedcommand
(bothObservable
).A simple property binding could be as follows:
button.bind( 'isEnabled' ).to( command, 'isEnabled' );
or even shorter:
button.bind( 'isEnabled' ).to( command );
which works in the following way:
button.isEnabled
instantly equalscommand.isEnabled
,- whenever
command.isEnabled
changes,button.isEnabled
will immediately reflect its value.
Note: To release the binding, use
unbind
.You can also "rename" the property in the binding by specifying the new name in the
to()
chain:button.bind( 'isEnabled' ).to( command, 'isWorking' );
It is possible to bind more than one property at a time to shorten the code:
button.bind( 'isEnabled', 'value' ).to( command );
which corresponds to:
button.bind( 'isEnabled' ).to( command ); button.bind( 'value' ).to( command );
The binding can include more than one observable, combining multiple data sources in a custom callback:
button.bind( 'isEnabled' ).to( command, 'isEnabled', ui, 'isVisible', ( isCommandEnabled, isUIVisible ) => isCommandEnabled && isUIVisible );
Using a custom callback allows processing the value before passing it to the target property:
button.bind( 'isEnabled' ).to( command, 'value', value => value === 'heading1' );
It is also possible to bind to the same property in an array of observables. To bind a
button
to multiple commands (alsoObservables
) so that each and every one of them must be enabled for the button to become enabled, use the following code:button.bind( 'isEnabled' ).toMany( [ commandA, commandB, commandC ], 'isEnabled', ( isAEnabled, isBEnabled, isCEnabled ) => isAEnabled && isBEnabled && isCEnabled );
Type parameters
K1
K2
Parameters
bindProperty1 : K1
Observable property that will be bound to other observable(s).
bindProperty2 : K2
Observable property that will be bound to other observable(s).
Returns
-
inherited
bind( bindProperty ) → SingleBindChain<K, Command[ K ]>
module:core/command~Command#bind:SINGLE_BIND
Binds observable properties to other objects implementing the
Observable
interface.Read more in the dedicated guide covering the topic of property bindings with some additional examples.
Consider two objects: a
button
and an associatedcommand
(bothObservable
).A simple property binding could be as follows:
button.bind( 'isEnabled' ).to( command, 'isEnabled' );
or even shorter:
button.bind( 'isEnabled' ).to( command );
which works in the following way:
button.isEnabled
instantly equalscommand.isEnabled
,- whenever
command.isEnabled
changes,button.isEnabled
will immediately reflect its value.
Note: To release the binding, use
unbind
.You can also "rename" the property in the binding by specifying the new name in the
to()
chain:button.bind( 'isEnabled' ).to( command, 'isWorking' );
It is possible to bind more than one property at a time to shorten the code:
button.bind( 'isEnabled', 'value' ).to( command );
which corresponds to:
button.bind( 'isEnabled' ).to( command ); button.bind( 'value' ).to( command );
The binding can include more than one observable, combining multiple data sources in a custom callback:
button.bind( 'isEnabled' ).to( command, 'isEnabled', ui, 'isVisible', ( isCommandEnabled, isUIVisible ) => isCommandEnabled && isUIVisible );
Using a custom callback allows processing the value before passing it to the target property:
button.bind( 'isEnabled' ).to( command, 'value', value => value === 'heading1' );
It is also possible to bind to the same property in an array of observables. To bind a
button
to multiple commands (alsoObservables
) so that each and every one of them must be enabled for the button to become enabled, use the following code:button.bind( 'isEnabled' ).toMany( [ commandA, commandB, commandC ], 'isEnabled', ( isAEnabled, isBEnabled, isCEnabled ) => isAEnabled && isBEnabled && isCEnabled );
Type parameters
K
Parameters
bindProperty : K
Observable property that will be bound to other observable(s).
Returns
SingleBindChain<K, Command[ K ]>
The bind chain with the
to()
andtoMany()
methods.
-
clearForceDisabled( id ) → void
module:core/command~Command#clearForceDisabled
Clears forced disable previously set through
forceDisabled
. SeeforceDisabled
.Parameters
id : string
Unique identifier, equal to the one passed in
forceDisabled
call.
Returns
void
-
Turns the given methods of this object into event-based ones. This means that the new method will fire an event (named after the method) and the original action will be plugged as a listener to that event.
Read more in the dedicated guide covering the topic of decorating methods with some additional examples.
Decorating the method does not change its behavior (it only adds an event), but it allows to modify it later on by listening to the method's event.
For example, to cancel the method execution the event can be stopped:
class Foo extends ObservableMixin() { constructor() { super(); this.decorate( 'method' ); } method() { console.log( 'called!' ); } } const foo = new Foo(); foo.on( 'method', ( evt ) => { evt.stop(); }, { priority: 'high' } ); foo.method(); // Nothing is logged.
Note: The high priority listener has been used to execute this particular callback before the one which calls the original method (which uses the "normal" priority).
It is also possible to change the returned value:
foo.on( 'method', ( evt ) => { evt.return = 'Foo!'; } ); foo.method(); // -> 'Foo'
Finally, it is possible to access and modify the arguments the method is called with:
method( a, b ) { console.log( `${ a }, ${ b }` ); } // ... foo.on( 'method', ( evt, args ) => { args[ 0 ] = 3; console.log( args[ 1 ] ); // -> 2 }, { priority: 'high' } ); foo.method( 1, 2 ); // -> '3, 2'
Parameters
methodName : 'off' | 'on' | 'once' | 'listenTo' | 'stopListening' | 'fire' | 'delegate' | 'stopDelegating' | 'set' | 'bind' | 'unbind' | 'decorate' | 'destroy' | 'value' | 'execute' | 'isEnabled' | 'affectsData' | 'refresh' | 'editor' | 'forceDisabled' | 'clearForceDisabled'
Name of the method to decorate.
Returns
void
-
Delegates selected events to another
Emitter
. For instance:emitterA.delegate( 'eventX' ).to( emitterB ); emitterA.delegate( 'eventX', 'eventY' ).to( emitterC );
then
eventX
is delegated (fired by)emitterB
andemitterC
along withdata
:emitterA.fire( 'eventX', data );
and
eventY
is delegated (fired by)emitterC
along withdata
:emitterA.fire( 'eventY', data );
Parameters
events : Array<string>
Event names that will be delegated to another emitter.
Returns
-
destroy() → void
module:core/command~Command#destroy
-
execute( args ) → unknown
module:core/command~Command#execute
Executes the command.
A command may accept parameters. They will be passed from
editor.execute()
to the command.The
execute()
method will automatically abort when the command is disabled (isEnabled
isfalse
). This behavior is implemented by a high priority listener to the event-execute event.In order to see how to disable a command from "outside" see the
isEnabled
documentation.This method may return a value, which would be forwarded all the way down to the
editor.execute()
.Parameters
args : Array<unknown>
Returns
unknown
Fires
-
inherited
fire( eventOrInfo, args ) → GetEventInfo<TEvent>[ 'return' ]
module:core/command~Command#fire
Fires an event, executing all callbacks registered for it.
The first parameter passed to callbacks is an
EventInfo
object, followed by the optionalargs
provided in thefire()
method call.Type parameters
Parameters
eventOrInfo : GetNameOrEventInfo<TEvent>
The name of the event or
EventInfo
object if event is delegated.args : TEvent[ 'args' ]
Additional arguments to be passed to the callbacks.
Returns
GetEventInfo<TEvent>[ 'return' ]
By default the method returns
undefined
. However, the return value can be changed by listeners through modification of theevt.return
's property (the event info is the first param of every callback).
-
forceDisabled( id ) → void
module:core/command~Command#forceDisabled
Disables the command.
Command may be disabled by multiple features or algorithms (at once). When disabling a command, unique id should be passed (e.g. the feature name). The same identifier should be used when enabling back the command. The command becomes enabled only after all features enabled it back.
Disabling and enabling a command:
command.isEnabled; // -> true command.forceDisabled( 'MyFeature' ); command.isEnabled; // -> false command.clearForceDisabled( 'MyFeature' ); command.isEnabled; // -> true
Command disabled by multiple features:
command.forceDisabled( 'MyFeature' ); command.forceDisabled( 'OtherFeature' ); command.clearForceDisabled( 'MyFeature' ); command.isEnabled; // -> false command.clearForceDisabled( 'OtherFeature' ); command.isEnabled; // -> true
Multiple disabling with the same identifier is redundant:
command.forceDisabled( 'MyFeature' ); command.forceDisabled( 'MyFeature' ); command.clearForceDisabled( 'MyFeature' ); command.isEnabled; // -> true
Note: some commands or algorithms may have more complex logic when it comes to enabling or disabling certain commands, so the command might be still disabled after
clearForceDisabled
was used.Parameters
id : string
Unique identifier for disabling. Use the same id when enabling back the command.
Returns
void
-
inherited
listenTo( emitter, event, callback, [ options ] ) → void
module:core/command~Command#listenTo:BASE_EMITTER
Registers a callback function to be executed when an event is fired in a specific (emitter) object.
Events can be grouped in namespaces using
:
. When namespaced event is fired, it additionally fires all callbacks for that namespace.// myEmitter.on( ... ) is a shorthand for myEmitter.listenTo( myEmitter, ... ). myEmitter.on( 'myGroup', genericCallback ); myEmitter.on( 'myGroup:myEvent', specificCallback ); // genericCallback is fired. myEmitter.fire( 'myGroup' ); // both genericCallback and specificCallback are fired. myEmitter.fire( 'myGroup:myEvent' ); // genericCallback is fired even though there are no callbacks for "foo". myEmitter.fire( 'myGroup:foo' );
An event callback can stop the event and set the return value of the
fire
method.Type parameters
Parameters
emitter : Emitter
The object that fires the event.
event : TEvent[ 'name' ]
The name of the event.
callback : GetCallback<TEvent>
The function to be called on event.
[ options ] : GetCallbackOptions<TEvent>
Additional options.
Returns
void
-
Stops executing the callback on the given event. Shorthand for
this.stopListening( this, event, callback )
.Parameters
event : string
The name of the event.
callback : Function
The function to stop being called.
Returns
void
-
Registers a callback function to be executed when an event is fired.
Shorthand for
this.listenTo( this, event, callback, options )
(it makes the emitter listen on itself).Type parameters
Parameters
event : TEvent[ 'name' ]
The name of the event.
callback : GetCallback<TEvent>
The function to be called on event.
[ options ] : GetCallbackOptions<TEvent>
Additional options.
Returns
void
-
Registers a callback function to be executed on the next time the event is fired only. This is similar to calling
on
followed byoff
in the callback.Type parameters
Parameters
event : TEvent[ 'name' ]
The name of the event.
callback : GetCallback<TEvent>
The function to be called on event.
[ options ] : GetCallbackOptions<TEvent>
Additional options.
Returns
void
-
refresh() → void
module:core/command~Command#refresh
Refreshes the command. The command should update its
isEnabled
andvalue
properties in this method.This method is automatically called when any changes are applied to the document.
Returns
void
-
Creates and sets the value of an observable properties of this object. Such a property becomes a part of the state and is observable.
It accepts a single object literal containing key/value pairs with properties to be set.
This method throws the
observable-set-cannot-override
error if the observable instance already has a property with the given property name. This prevents from mistakenly overriding existing properties and methods, but means thatfoo.set( 'bar', 1 )
may be slightly slower thanfoo.bar = 1
.In TypeScript, those properties should be declared in class using
declare
keyword. In example:public declare myProp1: number; public declare myProp2: string; constructor() { this.set( { 'myProp1: 2, 'myProp2: 'foo' } ); }
Parameters
values : object
An object with
name=>value
pairs.
Returns
void
-
Creates and sets the value of an observable property of this object. Such a property becomes a part of the state and is observable.
This method throws the
observable-set-cannot-override
error if the observable instance already has a property with the given property name. This prevents from mistakenly overriding existing properties and methods, but means thatfoo.set( 'bar', 1 )
may be slightly slower thanfoo.bar = 1
.In TypeScript, those properties should be declared in class using
declare
keyword. In example:public declare myProp: number; constructor() { this.set( 'myProp', 2 ); }
Type parameters
K
Parameters
name : K
The property's name.
value : Command[ K ]
The property's value.
Returns
void
-
Stops delegating events. It can be used at different levels:
- To stop delegating all events.
- To stop delegating a specific event to all emitters.
- To stop delegating a specific event to a specific emitter.
Parameters
[ event ] : string
The name of the event to stop delegating. If omitted, stops it all delegations.
[ emitter ] : Emitter
(requires
event
) The object to stop delegating a particular event to. If omitted, stops delegation ofevent
to all emitters.
Returns
void
-
inherited
stopListening( [ emitter ], [ event ], [ callback ] ) → void
module:core/command~Command#stopListening:BASE_STOP
Stops listening for events. It can be used at different levels:
- To stop listening to a specific callback.
- To stop listening to a specific event.
- To stop listening to all events fired by a specific object.
- To stop listening to all events fired by all objects.
Parameters
[ emitter ] : Emitter
The object to stop listening to. If omitted, stops it for all objects.
[ event ] : string
(Requires the
emitter
) The name of the event to stop listening to. If omitted, stops it for all events fromemitter
.[ callback ] : Function
(Requires the
event
) The function to be removed from the call list for the givenevent
.
Returns
void
-
Removes the binding created with
bind
.// Removes the binding for the 'a' property. A.unbind( 'a' ); // Removes bindings for all properties. A.unbind();
Parameters
unbindProperties : Array<'off' | 'on' | 'once' | 'listenTo' | 'stopListening' | 'fire' | 'delegate' | 'stopDelegating' | 'set' | 'bind' | 'unbind' | 'decorate' | 'destroy' | 'value' | 'execute' | 'isEnabled' | 'affectsData' | 'refresh' | 'editor' | 'forceDisabled' | 'clearForceDisabled'>
Observable properties to be unbound. All the bindings will be released if no properties are provided.
Returns
void
Events
-
change:isEnabled( eventInfo, name, value, oldValue )
module:core/command~Command#event:change:isEnabled
Fired when the
isEnabled
property changed value.Parameters
eventInfo : EventInfo
An object containing information about the fired event.
name : string
Name of the changed property (
isEnabled
).value : boolean
New value of the
isEnabled
property with given key ornull
, if operation should remove property.oldValue : boolean
Old value of the
isEnabled
property with given key ornull
, if property was not set before.
-
change:value( eventInfo, name, value, oldValue )
module:core/command~Command#event:change:value
Fired when the
value
property changed value.Parameters
eventInfo : EventInfo
An object containing information about the fired event.
name : string
Name of the changed property (
value
).value : unknown
New value of the
value
property with given key ornull
, if operation should remove property.oldValue : unknown
Old value of the
value
property with given key ornull
, if property was not set before.
-
inherited
change:{property}( eventInfo, name, value, oldValue )
module:core/command~Command#event:change:{property}
Fired when a property changed value.
observable.set( 'prop', 1 ); observable.on<ObservableChangeEvent<number>>( 'change:prop', ( evt, propertyName, newValue, oldValue ) => { console.log( `${ propertyName } has changed from ${ oldValue } to ${ newValue }` ); } ); observable.prop = 2; // -> 'prop has changed from 1 to 2'
Parameters
eventInfo : EventInfo
An object containing information about the fired event.
name : string
The property name.
value : TValue
The new property value.
oldValue : TValue
The previous property value.
-
execute( eventInfo, <anonymous> )
module:core/command~Command#event:execute
Event fired by the
execute
method. The command action is a listener to this event so it's possible to change/cancel the behavior of the command by listening to this event.See
decorate
for more information and samples.Note: This event is fired even if command is disabled. However, it is automatically blocked by a high priority listener in order to prevent command execution.
Parameters
eventInfo : EventInfo
An object containing information about the fired event.
<anonymous> : Parameters<TObservable[ TName ]>
-
set:isEnabled( eventInfo, name, value, oldValue )
module:core/command~Command#event:set:isEnabled
Fired when the
isEnabled
property is going to be set but is not set yet (before thechange
event is fired).Parameters
eventInfo : EventInfo
An object containing information about the fired event.
name : string
Name of the changed property (
isEnabled
).value : boolean
New value of the
isEnabled
property with given key ornull
, if operation should remove property.oldValue : boolean
Old value of the
isEnabled
property with given key ornull
, if property was not set before.
-
set:value( eventInfo, name, value, oldValue )
module:core/command~Command#event:set:value
Fired when the
value
property is going to be set but is not set yet (before thechange
event is fired).Parameters
eventInfo : EventInfo
An object containing information about the fired event.
name : string
Name of the changed property (
value
).value : unknown
New value of the
value
property with given key ornull
, if operation should remove property.oldValue : unknown
Old value of the
value
property with given key ornull
, if property was not set before.
-
inherited
set:{property}( eventInfo, name, value, oldValue )
module:core/command~Command#event:set:{property}
Fired when a property value is going to be set but is not set yet (before the
change
event is fired).You can control the final value of the property by using the event's
return
property.observable.set( 'prop', 1 ); observable.on<ObservableSetEvent<number>>( 'set:prop', ( evt, propertyName, newValue, oldValue ) => { console.log( `Value is going to be changed from ${ oldValue } to ${ newValue }` ); console.log( `Current property value is ${ observable[ propertyName ] }` ); // Let's override the value. evt.return = 3; } ); observable.on<ObservableChangeEvent<number>>( 'change:prop', ( evt, propertyName, newValue, oldValue ) => { console.log( `Value has changed from ${ oldValue } to ${ newValue }` ); } ); observable.prop = 2; // -> 'Value is going to be changed from 1 to 2' // -> 'Current property value is 1' // -> 'Value has changed from 1 to 3'
Note: The event is fired even when the new value is the same as the old value.
Parameters
eventInfo : EventInfo
An object containing information about the fired event.
name : string
The property name.
value : TValue
The new property value.
oldValue : TValue
The previous property value.
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