Javascript Angular2等待JSON文件加载
目前,我正在加载一个JSON文件,如下所示: 翻译服务 可本地化的.it.strings MyJavascript Angular2等待JSON文件加载,javascript,json,typescript,angular,Javascript,Json,Typescript,Angular,目前,我正在加载一个JSON文件,如下所示: 翻译服务 可本地化的.it.strings MyTranslationService被注入MyHomeComponent中,但问题是当我尝试通过管道读取这些值时,在呈现页面时仍需要加载这些值 翻译.pipe.ts 知道如何在加载任何页面之前加载JSON文件中的所有值吗?我认为您不应该尝试使代码同步。相反,让TranslationService告诉您何时准备就绪: export class TranslationService { // ...
TranslationService
被注入MyHomeComponent
中,但问题是当我尝试通过管道读取这些值时,在呈现页面时仍需要加载这些值
翻译.pipe.ts
知道如何在加载任何页面之前加载JSON文件中的所有值吗?我认为您不应该尝试使代码同步。相反,让
TranslationService
告诉您何时准备就绪:
export class TranslationService {
// ...
get isReady() {
return !!this._messages;
}
}
只有当\u messages
不为空时,管道才能返回翻译
export class TranslatePipe implements PipeTransform {
// ...
transform(value: string, args: string[]) : any {
return this._translation.isReady
? this._translation.getTranslationByKey(value) : null;
}
}
我认为您可以稍微调整一下您的服务和管道,以便在数据准备就绪/加载到后台时进行处理 首先添加一个observable,以便在数据加载到您的服务中时通知:
@Injectable()
export class TranslationService {
private _messages = {};
private translationLoaded : Observable<boolean>;
private translationLoadedObserver : Observer<boolean>;
constructor(private _http: Http) {
this.translationLoaded = Observable.create((observer) => {
this.translationLoadedObserver = observer;
});
var observable = this._http.get("app/i18n/localizable.it.strings").map((res: Response) => res.json());
observable.subscribe(res => {
this._messages = res;
this.translationLoadedObserver.next(true);
});
}
getTranslationByKey(key: string, args?: any[]) {
return this._messages[key];
}
}
这是对应的plunkr:。在这种情况下,在我加载的第一个页面上,它将始终返回null。否,只有在加载JSON之前,它才会为空,然后Angular将使用此管道自动更新所有表达式。最后,您可以使用
包装整个内容,在翻译准备就绪后将显示此内容。
export class TranslationService {
// ...
get isReady() {
return !!this._messages;
}
}
export class TranslatePipe implements PipeTransform {
// ...
transform(value: string, args: string[]) : any {
return this._translation.isReady
? this._translation.getTranslationByKey(value) : null;
}
}
@Injectable()
export class TranslationService {
private _messages = {};
private translationLoaded : Observable<boolean>;
private translationLoadedObserver : Observer<boolean>;
constructor(private _http: Http) {
this.translationLoaded = Observable.create((observer) => {
this.translationLoadedObserver = observer;
});
var observable = this._http.get("app/i18n/localizable.it.strings").map((res: Response) => res.json());
observable.subscribe(res => {
this._messages = res;
this.translationLoadedObserver.next(true);
});
}
getTranslationByKey(key: string, args?: any[]) {
return this._messages[key];
}
}
@Pipe({
name: 'translate',
pure: false // required to update the value when data are loaded
})
export class TranslatePipe implements PipeTransform {
constructor(private _ref :ChangeDetectorRef, private _translation: TranslationService) {
this.loaded = false;
}
transform(value: string, args: string[]) : any {
this.translationLoadedSub = this._translation.translationLoaded.subscribe((data) => {
this.value = this._translation.getTranslationByKey(value);
this._ref.markForCheck();
this.loaded = true;
});
if (this.value == null && this.loaded) {
this.value = this._translation.getTranslationByKey(value);
}
return this.value;
}
_dispose(): void {
if(isPresent(this.translationLoadedSub)) {
this.translationLoadedSub.unsubscribe();
this.translationLoadedSub = undefined;
}
}
ngOnDestroy(): void {
this._dispose();
}
}