Class ModelSchema

Creates a schema instance.

Allows registering a callback to the #checkAttribute method calls.

Callbacks allow you to implement rules which are not otherwise possible to achieve by using the declarative API of module:engine/model/schema~ModelSchemaItemDefinition.

Note that callback checks have bigger priority than declarative rules checks and may overwrite them.

For example, by using this method you can disallow setting attributes on nodes in specific contexts:

// Disallow setting `bold` on text inside `heading1` element:
schema.addAttributeCheck( context => {
	if ( context.endsWith( 'heading1 $text' ) ) {
		return false;
	}
}, 'bold' );
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You can skip the optional attributeName parameter to evaluate the callback for every checkAttribute() call.

// Disallow formatting attributes on text inside custom `myTitle` element:
schema.addAttributeCheck( ( context, attributeName ) => {
	if ( context.endsWith( 'myTitle $text' ) && schema.getAttributeProperties( attributeName ).isFormatting ) {
		return false;
	}
} );
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Please note that the generic callbacks may affect the editor performance and should be avoided if possible.

When one of the callbacks makes a decision (returns true or false) the processing is finished and other callbacks are not fired. Callbacks are fired in the order they were added, however generic callbacks are fired before callbacks added for a specified item.

You can also use #event:checkAttribute event, if you need even better control. The result from the example above could also be achieved with following event callback:

schema.on( 'checkAttribute', ( evt, args ) => {
	const context = args[ 0 ];
	const attributeName = args[ 1 ];

	if ( context.endsWith( 'myTitle $text' ) && schema.getAttributeProperties( attributeName ).isFormatting ) {
		// Prevent next listeners from being called.
		evt.stop();
		// Set the `checkAttribute()` return value.
		evt.return = false;
	}
}, { priority: 'high' } );
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Note that the callback checks and declarative rules checks are processed on normal priority.

Adding callbacks this way can also negatively impact editor performance.

Allows registering a callback to the #checkChild method calls.

Callbacks allow you to implement rules which are not otherwise possible to achieve by using the declarative API of module:engine/model/schema~ModelSchemaItemDefinition.

Note that callback checks have bigger priority than declarative rules checks and may overwrite them.

For example, by using this method you can disallow elements in specific contexts:

// Disallow `heading1` inside a `blockQuote` that is inside a table.
schema.addChildCheck( ( context, childDefinition ) => {
	if ( context.endsWith( 'tableCell blockQuote' ) ) {
		return false;
	}
}, 'heading1' );
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You can skip the optional itemName parameter to evaluate the callback for every checkChild() call.

// Inside specific custom element, allow only children, which allows for a specific attribute.
schema.addChildCheck( ( context, childDefinition ) => {
	if ( context.endsWith( 'myElement' ) ) {
		return childDefinition.allowAttributes.includes( 'myAttribute' );
	}
} );
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Please note that the generic callbacks may affect the editor performance and should be avoided if possible.

When one of the callbacks makes a decision (returns true or false) the processing is finished and other callbacks are not fired. Callbacks are fired in the order they were added, however generic callbacks are fired before callbacks added for a specified item.

You can also use checkChild event, if you need even better control. The result from the example above could also be achieved with following event callback:

schema.on( 'checkChild', ( evt, args ) => {
	const context = args[ 0 ];
	const childDefinition = args[ 1 ];

	if ( context.endsWith( 'myElement' ) ) {
		// Prevent next listeners from being called.
		evt.stop();
		// Set the `checkChild()` return value.
		evt.return = childDefinition.allowAttributes.includes( 'myAttribute' );
	}
}, { priority: 'high' } );
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Note that the callback checks and declarative rules checks are processed on normal priority.

Adding callbacks this way can also negatively impact editor performance.

Checks whether the given attribute can be applied in the given context (on the last item of the context).

schema.checkAttribute( textNode, 'bold' ); // -> false

schema.extend( '$text', {
	allowAttributes: 'bold'
} );

schema.checkAttribute( textNode, 'bold' ); // -> true
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Both module:engine/model/schema~ModelSchema#addAttributeCheck callback checks and declarative rules (added when module:engine/model/schema~ModelSchema#register registering and module:engine/model/schema~ModelSchema#extend extending items) are evaluated when this method is called.

Note that callback checks have bigger priority than declarative rules checks and may overwrite them.

Checks whether the attribute is allowed in selection:

• if the selection is not collapsed, then checks if the attribute is allowed on any of nodes in that range,
• if the selection is collapsed, then checks if on the selection position there's a text with the specified attribute allowed.

Checks whether the given node can be a child of the given context.

schema.checkChild( model.document.getRoot(), paragraph ); // -> false

schema.register( 'paragraph', {
	allowIn: '$root'
} );

schema.checkChild( model.document.getRoot(), paragraph ); // -> true
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Both module:engine/model/schema~ModelSchema#addChildCheck callback checks and declarative rules (added when module:engine/model/schema~ModelSchema#register registering and module:engine/model/schema~ModelSchema#extend extending items) are evaluated when this method is called.

Note that callback checks have bigger priority than declarative rules checks and may overwrite them.

Note that when verifying whether the given node can be a child of the given context, the schema also verifies the entire context – from its root to its last element. Therefore, it is possible for checkChild() to return false even though the context last element can contain the checked child. It happens if one of the context elements does not allow its child. When context is verified, module:engine/model/schema~ModelSchema#addChildCheck custom checks are considered as well.

Creates an instance of the schema context.

Extends a #register registered item's definition.

Extending properties such as allowIn will add more items to the existing properties, while redefining properties such as isBlock will override the previously defined ones.

schema.register( 'foo', {
	allowIn: '$root',
	isBlock: true;
} );
schema.extend( 'foo', {
	allowIn: 'blockQuote',
	isBlock: false
} );

schema.getDefinition( 'foo' );
//	{
//		allowIn: [ '$root', 'blockQuote' ],
// 		isBlock: false
//	}
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Tries to find position ancestors that allow to insert a given node. It starts searching from the given position and goes node by node to the top of the model tree as long as a module:engine/model/schema~ModelSchema#isLimit limit element, an module:engine/model/schema~ModelSchema#isObject object element or a topmost ancestor is not reached.

Returns a model range which is optimal (in terms of UX) for inserting a widget block.

For instance, if a selection is in the middle of a paragraph, the collapsed range before this paragraph will be returned so that it is not split. If the selection is at the end of a paragraph, the collapsed range after this paragraph will be returned.

Note: If the selection is placed in an empty block, the range in that block will be returned. If that range is then passed to module:engine/model/model~Model#insertContent, the block will be fully replaced by the inserted widget block.

Returns properties associated with a given model attribute. See #setAttributeProperties setAttributeProperties().

Gets attributes of a node that have a given property.

Returns a definition of the given item or undefined if an item is not registered.

This method should normally be used for reflection purposes (e.g. defining a clone of a certain element, checking a list of all block elements, etc). Use specific methods (such as #checkChild checkChild() or #isLimit isLimit()) in other cases.

Returns data of all registered items.

This method should normally be used for reflection purposes (e.g. defining a clone of a certain element, checking a list of all block elements, etc). Use specific methods (such as #checkChild checkChild() or #isLimit isLimit()) in other cases.

Returns the lowest module:engine/model/schema~ModelSchema#isLimit limit element containing the entire selection/range/position or the root otherwise.

Basing on given position, finds and returns a module:engine/model/range~ModelRange range which is nearest to that position and is a correct range for selection.

The correct selection range might be collapsed when it is located in a position where the text node can be placed. Non-collapsed range is returned when selection can be placed around element marked as an "object" in the module:engine/model/schema~ModelSchema schema.

Direction of searching for the nearest correct selection range can be specified as:

• both - searching will be performed in both ways,
• forward - searching will be performed only forward,
• backward - searching will be performed only backward.

When valid selection range cannot be found, null is returned.

Transforms the given set of ranges into a set of ranges where the given attribute is allowed (and can be applied).

Returns true if the given item is defined to be a block by the module:engine/model/schema~ModelSchemaItemDefinition's isBlock property.

schema.isBlock( 'paragraph' ); // -> true
schema.isBlock( '$root' ); // -> false

const paragraphElement = writer.createElement( 'paragraph' );
schema.isBlock( paragraphElement ); // -> true
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See the {@glink framework/deep-dive/schema#block-elements Block elements} section of the {@glink framework/deep-dive/schema Schema deep-dive} guide for more details.

Returns true if the given item is defined to be a content by the module:engine/model/schema~ModelSchemaItemDefinition's isContent property.

schema.isContent( 'paragraph' ); // -> false
schema.isContent( 'heading1' ); // -> false
schema.isContent( 'imageBlock' ); // -> true
schema.isContent( 'horizontalLine' ); // -> true

const text = writer.createText( 'foo' );
schema.isContent( text ); // -> true
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See the {@glink framework/deep-dive/schema#content-elements Content elements section} of the {@glink framework/deep-dive/schema Schema deep-dive} guide for more details.

Returns true if the given item is defined to be an inline element by the module:engine/model/schema~ModelSchemaItemDefinition's isInline property.

schema.isInline( 'paragraph' ); // -> false
schema.isInline( 'softBreak' ); // -> true

const text = writer.createText( 'foo' );
schema.isInline( text ); // -> true
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See the {@glink framework/deep-dive/schema#inline-elements Inline elements} section of the {@glink framework/deep-dive/schema Schema deep-dive} guide for more details.

Returns true if the given item should be treated as a limit element.

It considers an item to be a limit element if its module:engine/model/schema~ModelSchemaItemDefinition's module:engine/model/schema~ModelSchemaItemDefinition#isLimit isLimit or module:engine/model/schema~ModelSchemaItemDefinition#isObject isObject property was set to true.

schema.isLimit( 'paragraph' ); // -> false
schema.isLimit( '$root' ); // -> true
schema.isLimit( editor.model.document.getRoot() ); // -> true
schema.isLimit( 'imageBlock' ); // -> true
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See the {@glink framework/deep-dive/schema#limit-elements Limit elements} section of the {@glink framework/deep-dive/schema Schema deep-dive} guide for more details.

Returns true if the given item should be treated as an object element.

It considers an item to be an object element if its module:engine/model/schema~ModelSchemaItemDefinition's module:engine/model/schema~ModelSchemaItemDefinition#isObject isObject property was set to true.

schema.isObject( 'paragraph' ); // -> false
schema.isObject( 'imageBlock' ); // -> true

const imageElement = writer.createElement( 'imageBlock' );
schema.isObject( imageElement ); // -> true
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See the {@glink framework/deep-dive/schema#object-elements Object elements} section of the {@glink framework/deep-dive/schema Schema deep-dive} guide for more details.

Returns true if the given item is registered in the schema.

schema.isRegistered( 'paragraph' ); // -> true
schema.isRegistered( editor.model.document.getRoot() ); // -> true
schema.isRegistered( 'foo' ); // -> false
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Returns true if the given item is defined to be a selectable element by the module:engine/model/schema~ModelSchemaItemDefinition's isSelectable property.

schema.isSelectable( 'paragraph' ); // -> false
schema.isSelectable( 'heading1' ); // -> false
schema.isSelectable( 'imageBlock' ); // -> true
schema.isSelectable( 'tableCell' ); // -> true

const text = writer.createText( 'foo' );
schema.isSelectable( text ); // -> false
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See the {@glink framework/deep-dive/schema#selectable-elements Selectable elements section} of the {@glink framework/deep-dive/schema Schema deep-dive} guide for more details.

Registers a schema item. Can only be called once for every item name.

schema.register( 'paragraph', {
	inheritAllFrom: '$block'
} );
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Removes attributes disallowed by the schema.

Sets attributes allowed by the schema on a given node.

This method allows assigning additional metadata to the model attributes. For example, module:engine/model/schema~ModelAttributeProperties AttributeProperties#isFormatting property is used to mark formatting attributes (like bold or italic).

// Mark bold as a formatting attribute.
schema.setAttributeProperties( 'bold', {
	isFormatting: true
} );

// Override code not to be considered a formatting markup.
schema.setAttributeProperties( 'code', {
	isFormatting: false
} );
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Properties are not limited to members defined in the module:engine/model/schema~ModelAttributeProperties AttributeProperties type and you can also use custom properties:

schema.setAttributeProperties( 'blockQuote', {
	customProperty: 'value'
} );
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Subsequent calls with the same attribute will extend its custom properties:

schema.setAttributeProperties( 'blockQuote', {
	one: 1
} );

schema.setAttributeProperties( 'blockQuote', {
	two: 2
} );

console.log( schema.getAttributeProperties( 'blockQuote' ) );
// Logs: { one: 1, two: 2 }
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