[英]A state mutation was detected between dispatches but I haven't mutated state
我知道之前已经问过这个问题,但几乎所有人都在谈论OP直接改变状态,我试图避免使用像扩展运算符这样的技术(在对象和数组中),但尽管如此我得到以下错误:
Uncaught Error: A state mutation was detected between dispatches, in the path `courses.0`. This may cause incorrect behavior. (http://redux.js.org/docs/Troubleshooting.html#never-mutate-reducer-arguments)
at invariant (eval at <anonymous> (bundle.js:922), <anonymous>:40:15)
at eval (eval at <anonymous> (bundle.js:3825), <anonymous>:50:36)
at eval (eval at <anonymous> (bundle.js:3846), <anonymous>:14:16)
at dispatch (eval at <anonymous> (bundle.js:3853), <anonymous>:37:18)
at eval (eval at <anonymous> (bundle.js:1151), <anonymous>:63:5)
at eval (eval at <anonymous> (bundle.js:3846), <anonymous>:11:18)
at Object.eval [as saveCourse] (eval at <anonymous> (bundle.js:3860), <anonymous>:4:12)
at Object.ManageCoursePage._this.saveCourse [as onSave] (eval at <anonymous> (bundle.js:2080), <anonymous>:134:27)
at CourseForm._this.onHandleSave (eval at <anonymous> (bundle.js:2052), <anonymous>:93:19)
at Object.ReactErrorUtils.invokeGuardedCallback (eval at <anonymous> (bundle.js:1301), <anonymous>:69:16)
我读了错误指向的文章,因为它建议我检查我是否在我的reducer中手动改变状态,我看不到可能发生的地方:
const courseReducer = (state = initialState.courses, action) => {
switch (action.type) {
case types.LOAD_COURSE_SUCCESS:
return action.courses;
case types.CREATE_COURSE_SUCCESS:
//This action throw the error
debugger;
return [
...state,
Object.assign({}, action.course)
];
case types.UPDATE_COURSE_SUCCESS:
//This action throw the error
debugger;
return [
...state.filter(course => course.id !== action.course.id),
Object.assign({}, action.course)
];
case types.DELETE_COURSE_SUCCESS:
return [...state.filter(course => course.id !== action.courseId)];
default:
return state;
}
};
这是一个沙盒,其中包含可用于复制错误的应用程序的一部分 ,奇怪的是,这种情况只会在我创建新课程或尝试编辑现有课程时发生(在我的courseReducer
分别执行CREATE_COURSE_SUCCESS
和UPDATE_COURSE_SUCCESS
操作)
我真的很感激,如果有人能帮我弄清楚哪里可能是这个错误的根源。
问题是,你是变异状态,里面CoursesPage.js
,在mapStateToProps
:
let courses = state.courses.sort((c1, c2) =>
c1.title.localeCompare(c2.title, 'en', { sensitivity: 'base' }),
);
Array#sort
是一个就地操作 ,因此它通过对源数组进行排序来改变源数组。 这意味着, sort
正在改变state.courses
,从而导致错误。 相反,在排序之前,请复制state.courses
:
[...state.courses]
上面使用扩展语法将元素分散到一个新的数组中,基本上克隆它。 这与Array#slice
相同。 然后你可以这样排序:
let courses = [...state.courses].sort((c1, c2) =>
c1.title.localeCompare(c2.title, 'en', { sensitivity: 'base' }),
);
这不会改变原始的state.courses
并且不会抛出错误。
注:也有一些地方,你是变异this.state
直接,如在第32行ManageCoursePage.js
,你这样做:
this.state.errors = {}
只有在组件的构造函数中改变this.state
对象。 请改用setState
。
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