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[英]How this.setState() (react.Component method) has access of his child's class state?
[英]this.setState not working when a parent's state has to be updated by a child
所以我的应用程序中有一个父组件和一个子组件。 我想通过子组件更新父组件的状态,但它似乎不起作用。 我已经在Reactjs工作了很长时间,这对我来说很奇怪。 这是我的父组件的代码:
import React from 'react';
import { Stage } from 'react-konva';
import CircleComponent from './CircleComponent';
import LineComponent from './LineComponent';
import { getUserPlan } from '../../assets/UserPlan';
import { addColorClasses } from '../../helpers/utils';
class PortfolioMix extends React.Component {
constructor(props) {
super(props);
const data = addColorClasses(getUserPlan().plans[0]);
this.state = {
data: data,
circlePoints: []
};
this.getCirclePoints = this.getCirclePoints.bind(this);
}
getCirclePoints(points) {
this.setState({
circlePoints: points,
word: 'hello'
}, () => { console.log(this.state); });
}
processData() {
let data = this.state.data;
if(data[0].weight > 0.25 || (data[0].weight+data[1].weight) > 0.67) {
for(let i = 0; i < data.length; i++) {
data[i].weight /= 3;
}
}
return data;
}
render() {
const processedData = this.processData();
const firstCircle = processedData.splice(0,1);
const pmData = processedData.splice(0,this.state.data.length);
return(
<div>
<Stage
height={800}
width={1200}
style={{ backgroundColor: '#fff'}}>
<CircleComponent
x={1200/2}
y={800/2}
outerRadius={firstCircle[0].weight*1200}
outerColor={firstCircle[0].outerColor}
innerRadius={firstCircle[0].weight*1200*0.3}
innerColor={firstCircle[0].innerColor}
shadowColor={firstCircle[0].innerColor}
getCirclePoints={this.getCirclePoints}
/>
</Stage>
</div>
);
}
}
export default PortfolioMix;
这是子组件的代码:
class CircleComponent extends React.Component {
constructor(props) {
super(props);
this.state = {
points: this.getPoints(),
};
}
componentDidMount() {
this.props.getCirclePoints(this.state.points);
}
getPoints() {
const radius = this.props.outerRadius;
const x = this.props.x;
const y = this.props.y;
const points = [];
let angle = 0;
for(let i = 0; i < 8; i++) {
points.push({
pointX: x + radius * Math.cos(-angle * Math.PI / 180),
pointY: y + radius * Math.sin(-angle * Math.PI / 180)
});
angle += 42.5;
}
return points;
}
render() {
const {
x,
y,
outerRadius,
outerColor,
shadowColor,
innerRadius,
innerColor
} = this.props;
return (
<Layer>
<Group>
<Circle
x={x}
y={y}
radius={outerRadius}
fill={outerColor}
shadowBlur={5}
shadowColor={shadowColor}
/>
<Circle
x={x}
y={y}
radius={innerRadius}
fill={innerColor}
/>
</Group>
</Layer>
);
}
}
CircleComponent.propTypes = {
x: propTypes.number.isRequired,
y: propTypes.number.isRequired,
outerRadius: propTypes.number.isRequired,
outerColor: propTypes.string.isRequired,
shadowColor: propTypes.string,
innerRadius: propTypes.number.isRequired,
innerColor: propTypes.string.isRequired,
getCirclePoints: propTypes.func
};
export default CircleComponent;
现在,在父组件的getCirclePoints
方法中,我从子this.setState
获取点但是this.setState
不起作用。 正如您所看到的,我还将一个函数传递给this.setState
回调,它没有被调用,也没有将data
状态设置为空数组。 我最近4个小时一直在敲打这个问题。 任何形式的帮助表示赞赏。 我希望我身上没有一些愚蠢的错误。
在React文档中,您可以读到不应该直接修改状态,而只能使用setState()
方法修改状态。 您确实直接修改了PorfolioMix
状态两次:
在processData
:
data[i].weight /= 3;
在render
:
const processedData = this.processData(); const firstCircle = processedData.splice(0,1); const pmData = processedData.splice(0,this.state.data.length);
因为代码中的render
方法至少被调用两次, this.state.data
将是一个空数组,这会导致错误。
你可以在这里看到一个带有错误的实例: https : //jsfiddle.net/rhapLetv/
要修复它,您可以在processData
方法中返回数据的副本:
processData() {
const data = this.state.data;
if(data[0].weight > 0.25 || (data[0].weight+data[1].weight) > 0.67) {
return data.map(point => ({ ...point, weight: point.weight / 3 }))
} else {
return data.slice()
}
}
带修复程序的实例: https : //jsfiddle.net/rhapLetv/1/
您可以找到引入不可变数据的有用的immutable.js (或类似的库/帮助程序)。
你需要在方法processData()
.bind(this)
,因为React只会自动绑定(this)来渲染方法,构造函数和组件生命周期方法。
class PortfolioMix extends React.Component {
constructor(props) {
super(props);
const data = addColorClasses(getUserPlan().plans[0]);
this.state = {
data: data,
circlePoints: []
};
this.getCirclePoints = this.getCirclePoints.bind(this);
this.processData = this.processData.bind(this);
}
// ...
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