當涉及父/子關係時,您將在整個Angular源代碼中看到的常見模式是將自身添加爲自身提供者的父類型。這樣做是允許子組件注入父項。並且由於hierarchical DI,將只有一個父組件的實例下降組件樹。下面是什麼可能看起來像
export abstract class FormControlContainer {
abstract addControl(name: string, control: FormControl): void;
abstract removeControl(name: string): void;
}
export const formGroupContainerProvider: any = {
provide: FormControlContainer,
useExisting: forwardRef(() => NestedFormComponentsComponent)
};
@Component({
selector: 'nested-form-components',
template: `
...
`,
directives: [REACTIVE_FORM_DIRECTIVES, ChildComponent],
providers: [formGroupContainerProvider]
})
export class ParentComponent implements FormControlContainer {
form: FormGroup = new FormGroup({});
addControl(name: string, control: FormControl) {
this.form.addControl(name, control);
}
removeControl(name: string) {
this.form.removeControl(name);
}
}
的一些注意事項的例子:
我們正在使用的接口/抽象父(FormControlContainer
)爲一對夫婦的原因
- 它將
ParentComponent
從ChildComponent
中分離出來。孩子不需要知道任何關於具體的ParentComponent
。所有它知道的是FormControlContainer
和合同。
- 我們只通過接口合約在
ParentComponent
上公開方法。
我們只有做廣告ParentComponent
爲FormControlContainer
,那麼後者就是我們將注入。
我們以formControlContainerProvider
的形式創建提供商,然後將該提供商添加到ParentComponent
。由於分級DI,現在所有的孩子都可以訪問父母。
如果你不熟悉forwardRef
,this is a great article
在子女
現在,你可以做
@Component({
selector: 'child-component',
template: `
...
`,
directives: [REACTIVE_FORM_DIRECTIVES]
})
export class ChildComponent implements OnDestroy {
firstName: FormControl;
lastName: FormControl;
constructor(private _parent: FormControlContainer) {
this.firstName = new FormControl('', Validators.required);
this.lastName = new FormControl('', Validators.required);
this._parent.addControl('firstName', this.firstName);
this._parent.addControl('lastName', this.lastName);
}
ngOnDestroy() {
this._parent.removeControl('firstName');
this._parent.removeControl('lastName');
}
}
IMO,這是一個比經過FormGroup
更好的設計通過@Input
s。如前所述,這是整個Angular源代碼中的常見設計,所以我認爲可以肯定地說這是一個可接受的模式。
如果您想讓子組件更具可重用性,可以使構造函數參數@Optional()
。
下面是我用來測試上述實例
import {
Component, OnInit, ViewChildren, QueryList, OnDestroy, forwardRef, Injector
} from '@angular/core';
import {
FormControl,
FormGroup,
ControlContainer,
Validators,
FormGroupDirective,
REACTIVE_FORM_DIRECTIVES
} from '@angular/forms';
export abstract class FormControlContainer {
abstract addControl(name: string, control: FormControl): void;
abstract removeControl(name: string): void;
}
export const formGroupContainerProvider: any = {
provide: FormControlContainer,
useExisting: forwardRef(() => NestedFormComponentsComponent)
};
@Component({
selector: 'nested-form-components',
template: `
<form [formGroup]="form">
<child-component></child-component>
<div>
<button type="button" (click)="onSubmit()">Submit</button>
</div>
</form>
`,
directives: [REACTIVE_FORM_DIRECTIVES, forwardRef(() => ChildComponent)],
providers: [formGroupContainerProvider]
})
export class NestedFormComponentsComponent implements FormControlContainer {
form = new FormGroup({});
onSubmit(e) {
if (!this.form.valid) {
console.log('form is INVALID!')
if (this.form.hasError('required', ['firstName'])) {
console.log('First name is required.');
}
if (this.form.hasError('required', ['lastName'])) {
console.log('Last name is required.');
}
} else {
console.log('form is VALID!');
}
}
addControl(name: string, control: FormControl): void {
this.form.addControl(name, control);
}
removeControl(name: string): void {
this.form.removeControl(name);
}
}
@Component({
selector: 'child-component',
template: `
<div>
<label for="firstName">First name:</label>
<input id="firstName" [formControl]="firstName" type="text"/>
</div>
<div>
<label for="lastName">Last name:</label>
<input id="lastName" [formControl]="lastName" type="text"/>
</div>
`,
directives: [REACTIVE_FORM_DIRECTIVES]
})
export class ChildComponent implements OnDestroy {
firstName: FormControl;
lastName: FormControl;
constructor(private _parent: FormControlContainer) {
this.firstName = new FormControl('', Validators.required);
this.lastName = new FormControl('', Validators.required);
this._parent.addControl('firstName', this.firstName);
this._parent.addControl('lastName', this.lastName);
}
ngOnDestroy() {
this._parent.removeControl('firstName');
this._parent.removeControl('lastName');
}
}
如果你還在尋找一個答案,我發現這對我有幫助,特別是在卡拉的評論中發現的掠奪者:https://github.com/angular/angular/issues/9281#issuecomm ent-238610807 – cbros2008