javascript - 无法在 react 组件中设置状态

Question

我有一个 React 组件。我想在此组件中设置将传递给子组件的状态。我收到一个引用错误，我不确定为什么。

export const WidgetToolbar: React.FC<{}> = () => {

    this.state = {
        targetBox:null,
    }

    const isOpen = useBehavior(mainStore.isWidgetToolbarOpen);
    const themeClass = useBehavior(mainStore.themeClass);

    const userDashboards = useBehavior(dashboardStore.userDashboards);

    const [filter, setFilter] = useState("");
    const [sortOrder, setSortOrder] = useState<SortOrder>("asc");

    const userWidgets = useMemo(() => {
        let _userWidgets = values(userDashboards.widgets).filter((w) => w.widget.isVisible);

        if (sortOrder === "asc") {
            _userWidgets.sort((a, b) => a.widget.title.localeCompare(b.widget.title));
        } else {
            _userWidgets.sort((a, b) => b.widget.title.localeCompare(a.widget.title));
        }
        if (!isBlank(filter)) {
            _userWidgets = _userWidgets.filter((row) => {
                return row.widget.title.toLowerCase().includes(filter.toLocaleLowerCase());
            });
        }
        return _userWidgets;
    }, [userDashboards, sortOrder, filter]);
    ...

这是我遇到的错误:

TypeError: Cannot set property 'state' of undefined
    at WidgetToolbar (WidgetToolbar.tsx?ba4c:25)
    at ProxyFacade (react-hot-loader.development.js?439b:757)

Answer 1

功能组件中没有this 或this.state。使用 useState Hook ，类似于您在下面几行中所做的事情。

export const WidgetToolbar: React.FC<{}> = () => {
    const [targetBox, setTargetBox] = useState<null | whateverTheTypeIs>(null);

    //...

}