[英]Typescript, interfaces and variable declaration: what does it means?
这是 Material-UI 接口的一部分:
export interface DialogProps
extends StandardProps<ModalProps & Partial<TransitionHandlerProps>, DialogClassKey, 'children'> {
/**
* The id(s) of the element(s) that describe the dialog.
*/
/**
* If `true`, the dialog stretches to `maxWidth`.
*
* Notice that the dialog width grow is limited by the default margin.
*/
fullWidth?: boolean;
/**
* Determine the max-width of the dialog.
* The dialog width grows with the size of the screen.
* Set to `false` to disable `maxWidth`.
*/
maxWidth?: 'xs' | 'sm' | 'md' | 'lg' | 'xl' | false;
/**
* Callback fired when the backdrop is clicked.
*/
/**
* Props applied to the [`Transition`](http://reactcommunity.org/react-transition-group/transition#Transition-props) element.
*/
TransitionProps?: TransitionProps;
}
我尝试了以下分配(它有效:):
const maxWidth: DialogProps['maxWidth'] = 'lg'
我的问题是:这意味着什么? 我可以认为它声明了一个新变量,它是 DialogProps 的“子类型”吗? 我在哪里可以找到 typescript 中有关此主题的一些文档?
谢谢
当您像这样访问它时,您可以检索属性的类型: DialogProps['maxWidth']
export interface DialogProps {
/**
* The id(s) of the element(s) that describe the dialog.
*/
/**
* If `true`, the dialog stretches to `maxWidth`.
*
* Notice that the dialog width grow is limited by the default margin.
*/
fullWidth: boolean;
/**
* Determine the max-width of the dialog.
* The dialog width grows with the size of the screen.
* Set to `false` to disable `maxWidth`.
*/
maxWidth: 'xs' | 'sm' | 'md' | 'lg' | 'xl' | false;
}
const maxWidth: DialogProps.maxWidth = 'lg'
console.log(maxWidth);
如果您 hover 红色下划线文本,编译器实际上会告诉您您可以使用[propertyName]
检索属性的类型。
我自己不知道,文档在这里: https://github.com/Microsoft/TypeScript/blob/1db4f96fd14fc3de5ae3704e925afd6474cfb8f5/doc/spec.md#4.13
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