我正在尝试学习 angular 14 的变化,尤其是
inject()
功能,我可以将模块注入功能,我不需要为此创建特殊服务..但我想我做错了.
我正在尝试创建一些静态函数来使用包
ngx-toastr
发送零食消息,但这个包与我的问题无关。我如何正确地实现显示零食消息的功能,同时向它们注入它们需要操作的必需模块。
这是我的
messages.ts
文件:
import {inject} from '@angular/core';
import {ToastrService} from 'ngx-toastr';
export const snackMsgSuccess = (msg: string, title?: string) => {
const toaster = inject(ToastrService);
toaster.success(msg, title, {
easeTime: 1000
});
};
export const snackMsgInfo = (msg: string, title?: string) => {
const toaster = inject(ToastrService);
toaster.info(msg, title, {
easeTime: 1000
});
};
export const snackMsgWarn = (msg: string, title?: string) => {
const toaster = inject(ToastrService);
toaster.warning(msg, title, {
easeTime: 1000
});
};
export const snackMsgError = (msg: string, title?: string) => {
const toaster = inject(ToastrService);
toaster.error(msg, title, {
easeTime: 1000
});
};
我得到以下错误:
Error: Uncaught (in promise): Error: NG0203: inject() must be called from an injection context (a constructor, a factory function or a field initializer)
好吧......我之前有一个问题,当我试图有一个支持函数来获取路由参数时:
export const routeParam$ = (key: string) => {
const activatedRoute = inject(ActivatedRoute);
return activatedRoute.params.pipe(
pluck(key),
filter(r => r !== null),
distinctUntilChanged()
);
};
我只能在具有
task: Observable<string> = routeParam$('task');
的组件中用作字段初始值设定项
好吧,错误消息非常清楚……但仍然……我是 angular14 的新手,我认为注入可以让我做到这一点。否则对我来说没那么有用。
现在我把它作为一项服务..
import {Injectable} from '@angular/core';
import {ToastrService} from 'ngx-toastr';
@Injectable({
providedIn: 'root'
})
export class MsgService {
constructor(private toaster: ToastrService) {
}
public snackMsgSuccess = (msg: string, title?: string) => {
this.toaster.success(msg, title, {
easeTime: 1000
});
};
public snackMsgInfo = (msg: string, title?: string) => {
this.toaster.info(msg, title, {
easeTime: 1000
});
};
public snackMsgWarn = (msg: string, title?: string) => {
this.toaster.warning(msg, title, {
easeTime: 1000
});
};
public snackMsgError = (msg: string, title?: string) => {
this.toaster.error(msg, title, {
easeTime: 1000
});
};
}
但这是实现它的唯一方法吗?即使在 angular14 中?
如答案中所述,它只能在 DI 系统实例化依赖项期间初始化。您可以通过创建高阶函数来解决此问题。
export const snackMsgSuccess = () => {
const toaster = inject(ToastrService);
return (msg: string,title?: string)=>{
toaster.success(msg, title, {
easeTime: 1000
});
}
};
component.ts
snackMsgSuccess = snackMsgSuccess();
ngOnInit(){
this.snackMsgSuccess('Success','Test');
}
更新 Angular 14.1
在此版本中,可以使用 runInContext API 在函数体内使用注入函数。
在 v16+ 中使用 runInInjectionContext
injector = inject(EnvironmentInjector);
或
constructor(private injector: EnvironmentInjector)
然后
runInInjectionContext(this.injector, snackMsgSuccess);
从 Angular 14.1 开始,您可以使用 runInContext :
简单的例子:
class Foo {
constructor(private injector: EnvironmentInjector) {
setTimeout(() => {
// can't inject()
this.injector.runInContext(() => {
inject(MyService) // fine
});
}, 1000);
}
}