[英]setState() not triggering re-render
此代码有天生的错误吗?
有问题的部分是这样的:
// Update state and trigger re-render
// NOT WORKING
this.setState({ subsections });
调用setState()时未设置状态。 尽管数据在subsections
对象中。 我在其他方法上使用了相同的代码模式,并且按预期工作。
顺便说一下,如果我刷新页面,数据也会保存在Parse中。
import React from "react";
import Parse from 'parse';
import Subsections from './Subsections';
import AddSubsectionForm from './AddSubsectionForm';
class Manage extends React.Component {
constructor() {
super();
this.addSubsection = this.addSubsection.bind(this);
// Set initial state
this.state = {
subsections: {}
};
}
addSubsection(subsection) {
// Make copy of state
const subsections = {...this.state.subsections};
// Create new object
var SubsectionTest = Parse.Object.extend('SubsectionTest');
var subsectionTest = new SubsectionTest();
// Save object, then update state on return
subsectionTest.save({
name: subsection.name,
description: subsection.description
}).then(function(newSubsection) {
console.log('Has saved id of: '+newSubsection.id);
// Add new subsection to local state
subsections[newSubsection.id] = subsection;
// Log updatd subsections object
console.log(subsections);
// Update state and trigger re-render
// NOT WORKING
this.setState({ subsections });
},
function(error) {
console.log('Error:');
console.log(error);
});
}
/*
Loads subsections from Parse and displays them.
Code removed for clarity.
*/
componentWillMount() {
this.loadMenuItems();
}
render() {
if (this.state.subsections) {
return (
<div className="subsections">
<div className="mt3 border-top">
<h3 className="mt1 bold s2">Subsections</h3>
<div className="mt1">
<Subsections subsections={this.state.subsections} />
</div>
</div>
<div className="mt3 border-top">
<AddSubsectionForm addSubsection={this.addSubsection}/>
</div>
</div>
)
}
}
}
export default Manage;
您的问题是, this
不受您的promise的then
处理程序的约束:
}).then(function(newSubsection) {
由于您使用的ES2015班,你大概可以使用箭头功能(结合this
其词法范围):
}).then(newSubSection => {
另一个选择是显式绑定它:
}).then(function(newSubsection) {
...
}.bind(this));
上下文this
丢失,你可以尝试回调结合this
var callback = function (newSubsection) {
console.log('Has saved id of: ' + newSubsection.id);
.....
this.setState({
subsections
});
};
callback = callback.bind(this);
subsectionTest.save({
name: subsection.name,
description: subsection.description
}).then(callback),
function (error) {
console.log('Error:');
console.log(error);
});
如果您正在使用Babel预设阶段2 ,则可以使用箭头功能来实现
description: subsection.description
}).then(newSubsection = > {
console.log('Has saved id of: ' + newSubsection.id);
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