React setState不改变特定属性的状态

Question

我现在公司的一个旧开发人员最近把他的尾巴放在他的腿之间,并且在做了打字稿/反应后逃离,留下了一堆破碎的代码.

我现在的问题是我有这个TypeScript代码,只是从数组中删除一个项目并更改状态:

var currentFiles = this.state.openFiles;
    var index = this.state.openFiles.findIndex((f: IFileModel) => f.fileId == fileId)
    currentFiles.splice(index, 1);
    this.setState({ 
        mode: "gallery",
        openFiles: currentFiles 
    }, () => console.log(this.state.mode));

我的问题是状态永远不会更新mode,即使setState 应该这样做.无论我如何改变,console.log节目都是0.

即使在渲染函数中放置一个断点,mode也会告诉我0它应该在哪里"gallery".

这是初始状态:

this.state = {
            openFiles: [],
            mode: "gallery",
            categories: [],
            galleryState: {}
        }

有什么建议？

Answer 1

您在评论中说,您最近离开了该公司的开发人员已离开此代码.我担心他们给你的代码违反了React的两条规则:--)

1. 您无法直接修改状态,包括this.state引用的对象.你是这样做的currentFiles.splice(index, 1).

2. 您正在基于现有状态设置新状态,但不使用回调形式setState.

修复两者(见评论):

// Use the callback form that receives the up-to-date state as a parameter.
this.setState(
    ({openFiles}) => {
        var index = openFiles.findIndex((f: IFileModel) => f.fileId == fileId)
        // (Do you need an `if (index !== -1)` check here?)
        // Create a *new* array without the entry
        var currentFiles = [...openFiles.slice(0, index), ...openFiles.slice(index+1)];
        // Return the new state
        return {
            mode: "gallery",
            openFiles: currentFiles 
        };
    },
    () => console.log(this.state.mode)
);

更多在州文件.

实例:

class Example extends React.Component {
    constructor(...args) {
        super(...args);
        this.removeFileOnClick = this.removeFileOnClick.bind(this);
        this.state = {
            mode: "main",
            openFiles: [
                {fileId: 1, name: "File 1"},
                {fileId: 2, name: "File 2"},
                {fileId: 3, name: "File 3"},
                {fileId: 4, name: "File 4"},
                {fileId: 5, name: "File 5"}
            ]
        };
    }

    removeFileOnClick(e) {
        const fileId = e.currentTarget.getAttribute("data-id");
        this.setState(
            ({openFiles}) => {
                var index = openFiles.findIndex((f) => f.fileId == fileId)
                // (Do you need an `if (index !== -1)` check here?)
                // Create a *new* array without the entry
                var currentFiles = [...openFiles.slice(0, index), ...openFiles.slice(index+1)];
                // Return the new state
                return {
                    mode: "gallery",
                    openFiles: currentFiles 
                };
            },
            () => console.log(this.state.mode)
        );
    }

    render() {
        return ( 
            <div>
                Mode: {this.state.mode}
                <div>
                    OpenFiles ({this.state.openFiles.length}):
                    <div>{this.state.openFiles.map(file =>
                        <div><button data-id={file.fileId} onClick={this.removeFileOnClick}>X</button>{file.name}</div>
                    )}</div>
                </div>
            </div>
        );
    }
}

ReactDOM.render(
    <Example />,
    document.getElementById("root")
);

<div id="root"></div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.4.2/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.4.2/umd/react-dom.production.min.js"></script>

旁注:如果你不喜欢这里的双重传播:

var currentFiles = [...openFiles.slice(0, index), ...openFiles.slice(index+1)];

你可以这样做:

var currentFiles = openFiles.slice();
currentFiles.splice(index, 1);