Angular4 APP_INITIALIZER 不会延迟初始化 [英] Angular4 APP_INITIALIZER won't delay initialization
问题描述
打字稿:2.2.0角度:4.0
我试图通过使用 APP_INITIALIZER
确保在应用程序启动之前初始化 ConfigService
对象.我找到了很多关于如何执行此操作的示例,但是它们似乎都没有延迟应用程序的初始化.以下是我尝试实施的一些示例.
I am attempting to ensure that a ConfigService
object is initialized before application startup through the use of APP_INITIALIZER
. I've found many examples of how to do this however NONE of them seem to be delaying the initialization of the app. Here are just a handful of examples I've attempted to implement.
https://github.com/angular/angular/issues/9047https://gist.github.com/fernandohu/122e88c3bcd210bbe41c608c36306dbAngular2 APP_INITIALIZER 不一致
这是我的 NgModule
类
export function init(config: ConfigService) {
return () => {
config.load();
};
}
@NgModule({
declarations: [
AppComponent
],
imports: [
BrowserModule,
FormsModule,
HttpModule,
AppRoutingModule
],
providers: [
{
'provide': APP_INITIALIZER,
'useFactory': init,
'deps': [ConfigService],
'multi': true
},
ConfigService
],
bootstrap: [AppComponent]
})
export class AppModule {
}
这里是 ConfigService
类
@Injectable()
export class ConfigService {
private config: ApplicationConfiguration;
get apiRoot() {
return this.getProperty('apiRoot'); // <--- THIS GETS CALLED FIRST
}
constructor(private http: Http) {
}
load(): Promise<any> {
console.log('get user called');
const promise = this.http.get('./../../assets/config.json').map((res) => res.json()).toPromise();
promise.then(config => {
this.config = config; // <--- THIS RESOLVES AFTER
console.log(this.config);
});
return promise;
}
private getProperty(property: string): any {
//noinspection TsLint
if (!this.config) {
throw new Error(`Attempted to access configuration property before configuration data was loaded, please double check that 'APP_INITIALIZER is properly implemented.`);
}
if (!this.config[property]) {
throw new Error(`Required property ${property} was not defined within the configuration object. Please double check the
assets/config.json file`);
}
return this.config[property];
}
}
为了测试我将 ConfigService
注入到 AppComponent
中的所有内容.
And to test everything I've injected ConfigService
into AppComponent
with this.
import { Component } from '@angular/core';
import {ConfigService} from './services/config.service';
@Component({
selector: 'app-root',
templateUrl: './app.component.html',
styleUrls: ['./app.component.scss']
})
export class AppComponent {
title = 'app works!';
fullImagePath = '/src/image/avatar.jpeg';
constructor(private config: ConfigService) {
config.apiRoot;
}
}
推荐答案
你好像忘记从工厂返回值了:
Looks like you forgot to return value from factory:
export function init(config: ConfigService) {
return () => {
return config.load(); // add return
};
}
或者同样的代码可以稍微写一下:
or the same code can be written a bit shortly:
export function init(config: ConfigService) {
return () => config.load();
}
这篇关于Angular4 APP_INITIALIZER 不会延迟初始化的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!