将角度FormBuilder服务注入动态组件的方法

Question

我正在尝试通过以下方式将FormBuilder服务注入动态组件：

模板：

...
<div #vc></div>
...

组件：

@ViewChild('vc', { read: ViewContainerRef }) _container: ViewContainerRef;

...

  constructor(private fb: FormBuilder,
    private componentFactoryResolver: ComponentFactoryResolver,
    private _compiler: Compiler, private _injector: Injector,
    private _m: NgModuleRef<any>) {
  }

...

ngAfterViewInit() {
    let  allPms: any[] = null;
    let template = '';

    // construct template on the fly

    const wTypes = this._f.w_type;

    for (const plug of this._plugs) {
      if (plug.name === wTypes) {
        allPms = plug.params;
      }
    }

    for (const pm of allPms) {
      if (pm.type === 'str') {
        template = template + `
        <div class="form-group row">
          <label class="col-sm-3 col-form-label"><strong>` + pm.name + `</strong></label>
          <div class="col-sm-8">
            <input class="form-control" name="` + pm.name + `" type="text"
              formControlName="` + pm.name + `">
          </div>
        </div>
        `;
      }
    }

    // add field for each pm

    let injector1 = Injector.create([
      {
        provide: 'FormBuilder',
        useValue: FormBuilder
      }
    ]);

    const tmpCmp = Component({ template: template, styles: [`label {
      width: 128px;
      margin: 0px 8px;
    }`] })(class {
      constructor(private fb: FormBuilder) {
      }
    });
    const tmpModule = NgModule({ declarations: [tmpCmp] })(class {
    });

    this._compiler.compileModuleAndAllComponentsAsync(tmpModule)
      .then((factories) => {
        const f = factories.componentFactories[0];
        this.cmpRef = f.create(injector1, [], null, this._m);
        this.cmpRef.instance.name = 'B component';
        this._container.insert(this.cmpRef.hostView);
      })
  }

这样做，我得到了这个错误：

  ERROR Error: Can't resolve all parameters for class_1: (?).
    at syntaxError (compiler.js:1021)
    at CompileMetadataResolver.push../node_modules/@angular/compiler/fesm5/compiler.js.CompileMetadataResolver._getDependenciesMetadata (compiler.js:10922)
    at CompileMetadataResolver.push../node_modules/@angular/compiler/fesm5/compiler.js.CompileMetadataResolver._getTypeMetadata (compiler.js:10815)
    at CompileMetadataResolver.push../node_modules/@angular/compiler/fesm5/compiler.js.CompileMetadataResolver.getNonNormalizedDirectiveMetadata (compiler.js:10434)
    at CompileMetadataResolver.push../node_modules/@angular/compiler/fesm5/compiler.js.CompileMetadataResolver.loadDirectiveMetadata (compiler.js:10296)
    at compiler.js:23883
    at Array.forEach (<anonymous>)
    at compiler.js:23882
    at Array.forEach (<anonymous>)
    at JitCompiler.push../node_modules/@angular/compiler/fesm5/compiler.js.JitCompiler._loadModules (compiler.js:23879)
View_testComponent_17 @ testComponent.html:72
push../node_modules/@angular/core/fesm5/core.js.DebugContext_.logError @ core.js:11306
push../node_modules/@angular/core/fesm5/core.js.ErrorHandler.handleError @ core.js:1719
(anonymous) @ core.js:4578
./node_modules/zone.js/dist/zone.js.ZoneDelegate.invoke @ zone.js:391
./node_modules/zone.js/dist/zone.js.Zone.run @ zone.js:150
push../node_modules/@angular/core/fesm5/core.js.NgZone.runOutsideAngular @ core.js:3779
push../node_modules/@angular/core/fesm5/core.js.ApplicationRef.tick @ core.js:4578
(anonymous) @ core.js:4462
./node_modules/zone.js/dist/zone.js.ZoneDelegate.invoke @ zone.js:391
onInvoke @ core.js:3820

尝试添加自定义注射器没有帮助：

 let injector1 = Injector.create([
  {
    provide: 'FormBuilder',
    useValue: FormBuilder
  }
]);

以下是重现该问题的Stackblitz：

angular-dynamic-components-example

有什么办法解决这个问题？

Answer 1

?登录错误，例如Can't resolve all parameters for class_1: (?)，这意味着Angular无法解析传递给构造函数的参数类型。换句话说，反射器无法识别出private fb: FormBuilder参数具有FormBuilder类型，因为在TypeScript编译后类型会消失。

为了告诉TS编译器应保留此类型，您需要使用装饰器将此类定义重写为版本，例如：

@Component({
  template: template,
  styles: [
    `
      label {
        width: 128px;
        margin: 0px 8px;
      }
    `
  ]
})
class tmpCmp {
  constructor(private fb: FormBuilder) {}
}

Forked Stackblitz

它将被编译为：

tmpCmp = __decorate([
    core_1.Component({
        template: template,
        styles: [
            `
label {
width: 128px;
margin: 0px 8px;
}
`
        ]
    }),
    __metadata("design:paramtypes", [typeof (_a = typeof forms_1.FormBuilder !== "undefined" && forms_1.FormBuilder) === "function" ? _a : Object])
], tmpCmp);

您会注意到__metadata("design:paramtypes"部分负责向Angular反射器提供信息。

还有其他解决方法。

静态参数

const tmpCmp = Component({
  ...
})(
  class {
    constructor(private fb: FormBuilder) {}

    static parameters = [ FormBuilder ]
  }
);

Forked Stackblitz

静态ctorParameters方法

const tmpCmp = Component({
 ...
})(
  class {
    constructor(private fb: FormBuilder) {}

    static ctorParameters = () => [{ type: FormBuilder} ]
  }
);

Forked Stackblitz