英文:
How to define type to allow null in createContext React TypeScript?
问题
I have issue about typescript when creating modal context with typescript, I want to null as default value in createContext but it will causing typescript error
import React from 'react';type TModal = boolean;type TModalContext = [TModal, React.Dispatch<React.SetStateAction<TModal>>];const ModalContext = React.createContext<TModalContext | null>(null); // allow null as default valueconst ModalProvider = ({ children }: { children: React.ReactNode }) => {const modalState = useState<TModal>(false);return <ModalContext.Provider value={modalState}>{children}</ModalContext.Provider>;};const useModalContext = () => React.useContext(ModalContext);
When I call useModalContext hook to use in another component I get an error:
Type 'TModalContext | null' is not an array type.ts(2461)
How can I resolve this issue ?
英文:
I have issue about typescript when creating modal context with typescript, I want to null as default value in createContext but it will causing typescript error
import React from 'react';type TModal = boolean;type TModalContext = [TModal, React.Dispatch<React.SetStateAction<TModal>>];const ModalContext = React.createContext<TModalContext | null>(null); // allow null as defaut valueconst ModalProvider = ({ children }: { children: React.ReactNode }) => {const modalState = useState<TModal>(false);return <ModalContext.Provider value={modalState}>{children}</ModalContext.Provider>;};const useModalContext = () => React.useContext(ModalContext);
When I call useModalContext hook to use in another component I get an error:
> Type 'TModalContext | null' is not an array type.ts(2461)
const [isOpen, setOpen] = useModalContext();
How can I resolve this issue ?
答案1
得分: 1
Solution 1:
因为您告诉编译器 null 是一个有效的值，最简单的方法是在上下文为 null 时抛出一个 Error：
const useModalContext = () => {const context = React.useContext(ModalContext);if(context === null) throw new Error; // 或者在此处执行其他操作return context}
如果您始终在上下文内调用钩子，您就不必担心应用程序因 Error 而崩溃。
Solution 2:
另一方面，如果您无法确保钩子始终安全，您应该考虑处理来自调用者的 null 值：
const context = useModalContext();const [isOpen, setOpen] = context ?? []
英文:
Solution 1:
Because you tell the compile that null is a valid value, the most simple way is throw an Error when the context is null:
const useModalContext = () => {const context = React.useContext(ModalContext);if(context === null) throw new Error; // or do other things herereturn context}
You won't to worry about the app crashed by the Error if you always call the hook inside the context
Solution 2:
On the other hand, if you can't ensure the hook is always safe, you should consider handle the null value from the caller:
const context = useModalContext();const [isOpen, setOpen] = context ?? []
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