typescript 如何知道 ngOnChanges 中哪些@Input 发生了变化？
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How to know which @Input changes in ngOnChanges?
提问by Hongbo Miao
I am using Angular 2.
我正在使用 Angular 2。
Right now I have two @input aaand bb. I want to do:
现在我有两个 @inputaa和bb. 我想要做：
- If
aachanges, do something. - If
bbchanges, do other thing.
- 如果
aa发生变化，请做一些事情。 - 如果
bb发生变化，请做其他事情。
How to know which @Input changes in ngOnChanges? Thanks
如何知道哪个@Input 发生了变化ngOnChanges？谢谢
@Input() aa;
@Input() bb;
ngOnChanges(changes: { [propName: string]: SimpleChange }) {
// if aa changes, do something
// if bb changes, do other thing
}
回答by awiseman
Might be able to do it this way
也许可以这样做
ngOnChanges(changes: { [propName: string]: SimpleChange }) {
if( changes['aa'] && changes['aa'].previousValue != changes['aa'].currentValue ) {
// aa prop changed
}
if( changes['bb'] && changes['bb'].previousValue != changes['bb'].currentValue ) {
// bb prop changed
}
}
I'm surprised that the unchanged properties are defined, though. From the cookbook, I would expect that only changed properties would be defined.
不过，我很惊讶定义了未更改的属性。从食谱中，我希望只定义更改的属性。
https://angular.io/docs/ts/latest/cookbook/component-communication.html#!#parent-to-child-on-changes
https://angular.io/docs/ts/latest/cookbook/component-communication.html#!#parent-to-child-on-changes
If that is too verbose, you could also try using the setter approach:
如果这太冗长，您还可以尝试使用 setter 方法：
_aa: string;
_bb: string;
@Input() set aa(value: string) {
this._aa = value;
// do something on 'aa' change
}
@Input() set bb(value: string) {
this._bb = value;
// do something on 'bb' change
}
https://angular.io/docs/ts/latest/cookbook/component-communication.html#!#parent-to-child-setter
https://angular.io/docs/ts/latest/cookbook/component-communication.html#!#parent-to-child-setter
