Typechecking With PropTypes

类型检查是为了确保传入组件的参数正确性。

通常在项目中可以使用Flow或者TypeScript来实现。

React提供了PropTypes来检查类型。

示例：

import PropTypes from 'prop-types';

class Greeting extends React.Component {
 render() {
 return (
 <h1>Hello, {this.props.name}</h1>
 );
 }
}

Greeting.propTypes = {
 name: PropTypes.string
};

PropTypes

import PropTypes from 'prop-types';

MyComponent.propTypes = {
 // You can declare that a prop is a specific JS type. By default, these
 // are all optional.
 optionalArray: PropTypes.array,
 optionalBool: PropTypes.bool,
 optionalFunc: PropTypes.func,
 optionalNumber: PropTypes.number,
 optionalObject: PropTypes.object,
 optionalString: PropTypes.string,
 optionalSymbol: PropTypes.symbol,

 // Anything that can be rendered: numbers, strings, elements or an array
 // (or fragment) containing these types.
 optionalNode: PropTypes.node,

 // A React element.
 optionalElement: PropTypes.element,

 // You can also declare that a prop is an instance of a class. This uses
 // JS's instanceof operator.
 optionalMessage: PropTypes.instanceOf(Message),

 // You can ensure that your prop is limited to specific values by treating
 // it as an enum.
 optionalEnum: PropTypes.oneOf(['News', 'Photos']),

 // An object that could be one of many types
 optionalUnion: PropTypes.oneOfType([
 PropTypes.string,
 PropTypes.number,
 PropTypes.instanceOf(Message)
 ]),

 // An array of a certain type
 optionalArrayOf: PropTypes.arrayOf(PropTypes.number),

 // An object with property values of a certain type
 optionalObjectOf: PropTypes.objectOf(PropTypes.number),

 // An object taking on a particular shape
 optionalObjectWithShape: PropTypes.shape({
 color: PropTypes.string,
 fontSize: PropTypes.number
 }),

 // You can chain any of the above with `isRequired` to make sure a warning
 // is shown if the prop isn't provided.
 requiredFunc: PropTypes.func.isRequired,

 // A value of any data type
 requiredAny: PropTypes.any.isRequired,

 // You can also specify a custom validator. It should return an Error
 // object if the validation fails. Don't `console.warn` or throw, as this
 // won't work inside `oneOfType`.
 customProp: function(props, propName, componentName) {
 if (!/matchme/.test(props[propName])) {
 return new Error(
 'Invalid prop `' + propName + '` supplied to' +
 ' `' + componentName + '`. Validation failed.'
 );
 }
 },

 // You can also supply a custom validator to `arrayOf` and `objectOf`.
 // It should return an Error object if the validation fails. The validator
 // will be called for each key in the array or object. The first two
 // arguments of the validator are the array or object itself, and the
 // current item's key.
 customArrayProp: PropTypes.arrayOf(function(propValue, key, componentName, location, propFullName) {
 if (!/matchme/.test(propValue[key])) {
 return new Error(
 'Invalid prop `' + propFullName + '` supplied to' +
 ' `' + componentName + '`. Validation failed.'
 );
 }
 })
};

Requiring Single Child

import PropTypes from 'prop-types';

class MyComponent extends React.Component {
 render() {
 // This must be exactly one element or it will warn.
 const children = this.props.children;
 return (
 <p>
 {children}
 </p>
 );
 }
}

MyComponent.propTypes = {
 children: PropTypes.element.isRequired
};

Default Prop Values

class Greeting extends React.Component {
 render() {
 return (
 <h1>Hello, {this.props.name}</h1>
 );
 }
}

// Specifies the default values for props:
Greeting.defaultProps = {
 name: 'Stranger'
};

// Renders "Hello, Stranger":
ReactDOM.render(
 <Greeting />,
 document.getElementById('example')
);

以上内容在实现一个通用React组件时非常有用。类型检查和参数默认值一起使用，保证组件的正常运行。