如你所见,在渲染了当前视图的DOM更新之后,将调用AfterViewInit生命周期hook。如果我们更改这个hook中的值,它在第二次更改检测中将具有不同的值(如上所述,第二次检测在开发模式下是自动触发的),因此Angular将抛出ExpressionChangedAfterCheckedError。 我强烈建议你阅读Max Koretskyi撰写的《Angular更改检测全面解析》,它...
Expression has changed after it was checked. Previous value: “textContent: 1542375826274”. Current value: “textContent: 1542375826275”. 这条错误信息告诉我们由表达式生成的用于textContent绑定的值是不同的。是的,毫秒数的确不同。所以 Angular 评估了表达式time | date:’hh:mm:ss:SSS两次并比较了两次的...
如你所见,在渲染了当前视图的 DOM 更新之后,将调用 AfterViewInit 生命周期 hook。如果我们更改这个 hook 中的值,它在第二次更改检测中将具有不同的值(如上所述,第二次检测在开发模式下是自动触发的),因此 Angular 将抛出 ExpressionChangedAfterCheckedError。 我强烈建议你阅读 Max Koretskyi 撰写的《Angular 更...
ERROR Error: ExpressionChangedAfterItHasBeenCheckedError: Expression has changed after it was checked. Previous value: 'undefined'. Current value: 'test'. It seems like the view has been created after its parent and its children have been dirty checked. Has it been created in a change detectio...
Next (and only in dev mode), we run a second pass (checkNoChanges mode) and compare the values in the application to the values in the DOM. If any of them differ, we know that a change was made to the application's value after we had already rendered it. This is where we throw...
template:9:16 caused by: Expression has changed after it was checked. Previous value: 'undefined'. Current value: '[object Object]'.该错误仅在开发模式下会报告出来的,解决掉总是更好的选择,防止在生产环境下出现问题。问题的原因及解决办法这个问题是ng2中的变更检测策略造成的,ng2并没有智能到一有数...
UsedetectChanges()when you've updated the model after angular has run it's change detection, or if the update hasn't been in angular world at all. UsemarkForCheck()if you're usingOnPushand you're bypassing theChangeDetectionStrategyby mutating some data or you've updated the model inside ...
AfterViewInit AfterViewChecked OnDestroy 如果加上组件 constructor 那就是 9 个钩子。 Constructor 阶段 想要深入理解组件生命周期钩子,最简单的方法自然是逛源码咯。 经历过了Change Detection和NodeInjector两篇文章。我相信大家对 bootstrapApplication 函数已经不陌生了,那我们直接进入重点吧。
Although the notorious ExpressionChangedAfterItHasBeenCheckedError error in Angular can seem frustrating at times, it can be resolved pretty easily. Let's see how.
console.log('value changed', [before, after]);//['b', 'a']}) value= 'b'; 上面这段代码是不成立的。 常规思路 通常我们能想到 2 种方式去去解决这个问题。 第一种是把 value 变成一个对象,因为对象可以搞Proxy。通过拦截 setter 我们就能监听到了 value 每次的变化。