为什么我会收到"TypeEror:无法冻结"？

Question

我正在开发一个使用ngrx存储和效果的角度应用程序.我明白了

"TypeError:无法冻结"

从我的组件调度操作时出错.我写了一个文件上传功能.我认为我正在改变状态,但无法弄清楚在哪里以及如何解决它.这是我的详细代码:

Actions:

export enum FileUploadActionTypes {
    UploadFile = '[File Upload] Upload File',
    UploadFileSuccess = '[File Upload] Upload File Success',
    UploadFileFailure = '[File Upload] Upload File Failure'
}

export class UploadFile implements Action {
    readonly type = FileUploadActionTypes.UploadFile;

    constructor(public payload: any) {}
}

export class UploadFileSuccess implements Action {
    readonly type = FileUploadActionTypes.UploadFileSuccess;

    constructor(public payload: any) {}
}

export class UploadFileFailure implements Action {
    readonly type = FileUploadActionTypes.UploadFileFailure;

    constructor(public payload: any) {}
}

export type FileUploadActionsUnion = UploadFile | UploadFileSuccess | UploadFileFailure;

Service:

export class FileUploadService {
    constructor(private httpClient: HttpClient) {

    }
    uploadFile(file: any): Observable<any> {
        return this.httpClient.post<any[]>('/api-url/', file);
    }
}

Effect:

@Effect()
uploadFile$ = this.actions$.pipe(
    ofType<UploadFile>(FileUploadActionTypes.UploadFile),
    mergeMap(action => this.fileUploadService.uploadFile(action.payload).pipe(
        map(result => new UploadFileSuccess(result)),
        catchError(error => of(new UploadFileFailure(error)))
    ))
)

Reducer:

export interface State {
    fileUploadSuccessResponse: any,
    fileUploadFailureResponse: any
}

export const initialState = {
    fileUploadSuccessResponse: null,
    fileUploadFailureResponse: null
}

export const getFileUploadSuccessResponse = state => state.fileUploadSuccessResponse;
export const getFileUploadFailureResponse = state => state.fileUploadFailureResponse;

export function reducer(state: State = initialState, action: FileUploadActionsUnion):State {
    switch(action.type) {
        case FileUploadActionTypes.UploadFile: {
            return {
                ...state
            }
        }
        case FileUploadActionTypes.UploadFileSuccess: {
            return {
                ...state,
                fileUploadSuccessResponse: action.payload
            }
        }
        case FileUploadActionTypes.UploadFileFailure: {
            return {
                ...state,
                fileUploadFailureResponse: action.payload
            }
        }
        default: {
            return state;
        }
    }
}

Answer 1

看来您正在使用ngrx-store-freezenpm 包。此包可确保您对商店所做的任何更新都不会直接发生变异。此过程的一部分是将 anObject.freeze()应用于payload您尝试分派的操作的对象。即this.store.dispatch(new UploadFiles(file))。

<input type="file">控件的默认行为是将其值保存为FileList对象。由于此对象是原始数据类型，Javascript 会将其视为只读，从而阻止您写入其属性。这也解释了为什么Object.freeze()失败，因为它不能对只读数据类型应用冻结。

我最近在使用 NGRX 和<input type="file">表单控件时遇到了同样的问题。修复方法是FileList在分派到商店之前将其克隆到一个新对象中。

onChange(control: FormControl) {
  const primitiveFileList: FileList = control.value;
  const clonedFiles = { ...primitiveFileList };
  this.store.dispatch(new UploadFiles(clonedFiles));
}

如果其他人知道这种方法有任何潜在的缺点，我会很感激你的意见。