[英]Angular2: What does paired selector do in @Directive
I have some question about @directive of angular 2, 我对角2的@directive有疑问
I'm following this tutorial 我正在关注本教程
1- If selector has to be like this: 1-如果选择器必须像这样:
selector: '[validateEqual][formControlName],[validateEqual][formControl]
and validateEqual is has to be in constructor like this 和validateEqual是必须在这样的构造函数中
constructor( @Attribute('validateEqual') public validateEqual: string,
@Attribute('reverse') public reverse: string) {
}
what does it mean also What is @Attribute 这也意味着什么@Attribute
also if there is multi = true in provider and useExisting 同样在提供者和useExisting中是否有multi = true
selector: this means that the directive matches elements that have the attribute validateEqual
and one of formControlName
or formControl
选择器:这意味着指令匹配具有属性
validateEqual
以及formControlName
或formControl
之一的formControl
@Attribute
injects the value of an static attribute. @Attribute
注入静态属性的值。 Normally attributes are read into a directive using @Input()
. 通常,使用
@Input()
将属性读入指令。 @Input()
also supports bindings where the input is updated when the value bound to a property (or attribute changes). @Input()
还支持绑定,当绑定到属性的值(或属性更改)时,输入会更新。 @Input()
values are available in ngOnInit()
or ngOnChanges()
while values injected with @Attribute()
are available in the constructor but aren't updated if they change later. @Input()
值在ngOnInit()
或ngOnChanges()
中可用,而使用@Attribute()
注入的值在构造函数中可用,但是如果以后更改,则不会更新。
With the following code @Attribute('validateEqual') would set
public validateEqual to
foo` 使用以下代码,
@Attribute('validateEqual') would set
public validateEqual @Attribute('validateEqual') would set
to
foo`。
<div validateEqual="foo" formControlName="bar">
<!-- this doesn't work with `@Attribute('validateEqual')`
because the attribute value is not static -->
<div [validateEqual]="foo" formControlName="bar">
multi: true
means that one provider token provides an array of elements. multi: true
表示一个提供者令牌提供了一组元素。 For example all directives for router support routerLink
, router-outlet
are provided by ROUTER_DIRECTIVES
. routerLink
, router-outlet
由ROUTER_DIRECTIVES
提供。 ROUTER_DIRECTIVES
, then it overrides the previously registered directives. ROUTER_DIRECTIVES
注册了新的提供程序,则它将覆盖以前注册的指令。 If multi: true
(on the first registered and tjhe new provider) is set, the new directives are added to the previously registered directives instead of overriding. multi: true
(上注册的第一和 tjhe新提供商)设置,新指令将被添加到先前注册的指令,而不是压倒一切。 ROUTER_DIRECTIVES
is injected ( constructor(@Inject(ROUTER_DIRECTIVES) directives) {}
) an array of directive instances is injected. ROUTER_DIRECTIVES
( constructor(@Inject(ROUTER_DIRECTIVES) directives) {}
)时,将注入一系列指令实例。 It usually doesn't make sense to inject ROUTER_DIRECTIVES
. ROUTER_DIRECTIVES
通常没有任何意义。 I used it just as an example because it is multi: true
. multi: true
。
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