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ng_switch.ts
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ng_switch.ts
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/**
* @license
* Copyright Google Inc. All Rights Reserved.
*
* Use of this source code is governed by an MIT-style license that can be
* found in the LICENSE file at https://angular.io/license
*/
import {Directive, DoCheck, Host, Input, TemplateRef, ViewContainerRef} from '@angular/core';
export class SwitchView {
private _created = false;
constructor(
private _viewContainerRef: ViewContainerRef, private _templateRef: TemplateRef<Object>) {}
create(): void {
this._created = true;
this._viewContainerRef.createEmbeddedView(this._templateRef);
}
destroy(): void {
this._created = false;
this._viewContainerRef.clear();
}
enforceState(created: boolean) {
if (created && !this._created) {
this.create();
} else if (!created && this._created) {
this.destroy();
}
}
}
/**
* @ngModule CommonModule
*
* @usageNotes
* ```
* <container-element [ngSwitch]="switch_expression">
* <some-element *ngSwitchCase="match_expression_1">...</some-element>
* <some-element *ngSwitchCase="match_expression_2">...</some-element>
* <some-other-element *ngSwitchCase="match_expression_3">...</some-other-element>
* <ng-container *ngSwitchCase="match_expression_3">
* <!-- use a ng-container to group multiple root nodes -->
* <inner-element></inner-element>
* <inner-other-element></inner-other-element>
* </ng-container>
* <some-element *ngSwitchDefault>...</some-element>
* </container-element>
* ```
* @description
*
* Adds / removes DOM sub-trees when the nest match expressions matches the switch expression.
*
* `NgSwitch` stamps out nested views when their match expression value matches the value of the
* switch expression.
*
* In other words:
* - you define a container element (where you place the directive with a switch expression on the
* `[ngSwitch]="..."` attribute)
* - you define inner views inside the `NgSwitch` and place a `*ngSwitchCase` attribute on the view
* root elements.
*
* Elements within `NgSwitch` but outside of a `NgSwitchCase` or `NgSwitchDefault` directives will
* be preserved at the location.
*
* The `ngSwitchCase` directive informs the parent `NgSwitch` of which view to display when the
* expression is evaluated.
* When no matching expression is found on a `ngSwitchCase` view, the `ngSwitchDefault` view is
* stamped out.
*
* @stable
*/
@Directive({selector: '[ngSwitch]'})
export class NgSwitch {
private _defaultViews: SwitchView[];
private _defaultUsed = false;
private _caseCount = 0;
private _lastCaseCheckIndex = 0;
private _lastCasesMatched = false;
private _ngSwitch: any;
@Input()
set ngSwitch(newValue: any) {
this._ngSwitch = newValue;
if (this._caseCount === 0) {
this._updateDefaultCases(true);
}
}
/** @internal */
_addCase(): number { return this._caseCount++; }
/** @internal */
_addDefault(view: SwitchView) {
if (!this._defaultViews) {
this._defaultViews = [];
}
this._defaultViews.push(view);
}
/** @internal */
_matchCase(value: any): boolean {
const matched = value == this._ngSwitch;
this._lastCasesMatched = this._lastCasesMatched || matched;
this._lastCaseCheckIndex++;
if (this._lastCaseCheckIndex === this._caseCount) {
this._updateDefaultCases(!this._lastCasesMatched);
this._lastCaseCheckIndex = 0;
this._lastCasesMatched = false;
}
return matched;
}
private _updateDefaultCases(useDefault: boolean) {
if (this._defaultViews && useDefault !== this._defaultUsed) {
this._defaultUsed = useDefault;
for (let i = 0; i < this._defaultViews.length; i++) {
const defaultView = this._defaultViews[i];
defaultView.enforceState(useDefault);
}
}
}
}
/**
* @ngModule CommonModule
*
* @usageNotes
* ```
* <container-element [ngSwitch]="switch_expression">
* <some-element *ngSwitchCase="match_expression_1">...</some-element>
* </container-element>
*```
* @description
*
* Creates a view that will be added/removed from the parent {@link NgSwitch} when the
* given expression evaluate to respectively the same/different value as the switch
* expression.
*
* Insert the sub-tree when the expression evaluates to the same value as the enclosing switch
* expression.
*
* If multiple match expressions match the switch expression value, all of them are displayed.
*
* See {@link NgSwitch} for more details and example.
*
* @stable
*/
@Directive({selector: '[ngSwitchCase]'})
export class NgSwitchCase implements DoCheck {
private _view: SwitchView;
@Input()
ngSwitchCase: any;
constructor(
viewContainer: ViewContainerRef, templateRef: TemplateRef<Object>,
@Host() private ngSwitch: NgSwitch) {
ngSwitch._addCase();
this._view = new SwitchView(viewContainer, templateRef);
}
ngDoCheck() { this._view.enforceState(this.ngSwitch._matchCase(this.ngSwitchCase)); }
}
/**
* @ngModule CommonModule
* @usageNotes
* ```
* <container-element [ngSwitch]="switch_expression">
* <some-element *ngSwitchCase="match_expression_1">...</some-element>
* <some-other-element *ngSwitchDefault>...</some-other-element>
* </container-element>
* ```
*
* @description
*
* Creates a view that is added to the parent {@link NgSwitch} when no case expressions
* match the switch expression.
*
* Insert the sub-tree when no case expressions evaluate to the same value as the enclosing switch
* expression.
*
* See {@link NgSwitch} for more details and example.
*
* @stable
*/
@Directive({selector: '[ngSwitchDefault]'})
export class NgSwitchDefault {
constructor(
viewContainer: ViewContainerRef, templateRef: TemplateRef<Object>,
@Host() ngSwitch: NgSwitch) {
ngSwitch._addDefault(new SwitchView(viewContainer, templateRef));
}
}