我在看Pluralsight关于React的课程,老师说道具不应该被改变。我现在正在读一篇关于道具vs.国家的文章(uberVU/react-guide),它说
道具和状态更改都会触发呈现更新。
文章后面说:
Props(属性的缩写)是组件的配置,如果可以的话,是它的选项。它们是从上面接收的,是不可变的。
所以道具可以改变,但它们应该是不可变的?
什么时候应该使用道具,什么时候应该使用状态?
如果你有一个React组件需要的数据,它应该通过道具或设置在React组件通过getInitialState?
道具和状态是相关的。一个组件的状态通常会成为子组件的道具。道具在父元素的呈现方法中作为React.createElement()的第二个参数传递给子元素,如果您使用的是JSX,则是更熟悉的标记属性。
<MyChild name={this.state.childsName} />
父类的childsName的状态值变成子类的this.props.name。从子进程的角度来看,名称道具是不可变的。如果它需要改变,父进程只需要改变它的内部状态:
this.setState({ childsName: 'New name' });
React会把它传播给你的子程序。一个自然的后续问题是:如果子程序需要更改其名称道具怎么办?这通常是通过子事件和父回调完成的。子进程可能会公开一个名为onNameChanged的事件。然后父进程通过传递回调处理程序来订阅事件。
<MyChild name={this.state.childsName} onNameChanged={this.handleName} />
子进程将通过调用this.props将其请求的新名称作为参数传递给事件回调。onNameChanged('New name'),父进程将在事件处理程序中使用该名称来更新其状态。
handleName: function(newName) {
this.setState({ childsName: newName });
}
亲子交流,只需传递道具即可。
使用state在控制器视图中存储当前页面所需的数据。
使用道具将数据和事件处理程序传递给你的子组件。
这些列表应该有助于指导您在组件中处理数据。
道具
是不可变的
它可以让React进行快速参考检查
用于从视图控制器向下传递数据
顶级组件
有更好的表现
使用它将数据传递给子组件
状态
是否应该在视图控制器中进行管理
顶级组件
是可变的
表现更差
不应该从子组件访问
用道具把它传下去
For communication between two components that don't have a
parent-child relationship, you can set up your own global event
system. Subscribe to events in componentDidMount(), unsubscribe in
componentWillUnmount(), and call setState() when you receive an event.
Flux pattern is one of the possible ways to arrange this.
- https://facebook.github.io/react/tips/communicate-between-components.html
What Components Should Have State?
Most of your components should simply take some data from props and
render it. However, sometimes you need to respond to user input, a
server request or the passage of time. For this you use state.
Try to keep as many of your components as possible stateless. By doing
this you'll isolate the state to its most logical place and minimize
redundancy, making it easier to reason about your application.
A common pattern is to create several stateless components that just
render data, and have a stateful component above them in the hierarchy
that passes its state to its children via props. The stateful
component encapsulates all of the interaction logic, while the
stateless components take care of rendering data in a declarative way.
- https://facebook.github.io/react/docs/interactivity-and-dynamic-uis.html#what-components-should-have-state
What Should Go in State?
State should contain data that a component's event handlers may change
to trigger a UI update. In real apps this data tends to be very small
and JSON-serializable. When building a stateful component, think about
the minimal possible representation of its state, and only store those
properties in this.state. Inside of render() simply compute any other
information you need based on this state. You'll find that thinking
about and writing applications in this way tends to lead to the most
correct application, since adding redundant or computed values to
state means that you need to explicitly keep them in sync rather than
rely on React computing them for you.
- https://facebook.github.io/react/docs/interactivity-and-dynamic-uis.html#what-should-go-in-state
摘自:Andrea Chiarelli的书《开始React:用React简化前端开发工作流,增强应用程序的用户体验》:
Every React component has a props property. The purpose of this property is to collect data input passed to the component itself. JSX attribute is attached to a React element, a property with the same name is attached to the props object. So, we can access the passed data by using the attached property. In addition, the immutability of props allows us to think of components as pure functions, which are functions that have no side effects (since they don't change their input data). We can think of data passing from one component to another as a unidirectional data flow, from the parent component toward the child components. This gives us a more controllable system.
React provides a mechanism to support the automatic rendering of a component when data changes. Such a mechanism is based on the concept of state. React state is a property that represents data that changes over time. Every component supports the state property, but it should be used carefully. Components that store data that can change over time are said to be stateful components. A stateful component stores the state in the this.state property. To inform a component that the state has changed, you must use the setState() method. State initialization is the only case where you can assign a value to the this.state property without using setState().
setState()将新数据与已包含在状态中的旧数据合并,并覆盖先前的状态
setState()会触发render()方法的执行,所以永远不要显式地调用render()