state

问题 I am making an app that gets an array of news items from a remote source and displays them on a page. I have the endpoint, and can make a successful call, proven by console logs, using $.getJSON() . I placed this call into the parent component, because child components will need to use the data. However, when I pass this data down to a child component, the console error appears: Uncaught TypeError: Cannot read property 'headline' of undefined This is because React is trying to render the

问题 I'm facing issue in my current project so created this question im unable to get same bloc state in other widget i tried this https://github.com/felangel/bloc/issues/74#issuecomment-457968962 but i'm getting BlocProvider.of() called with a context that does not contain a Bloc of type CounterBloc. error if add Provider again in other widget another state is created for that page how to use same bloc state in different widgets. import 'dart:async'; import 'package:flutter/material.dart'; import

问题 I'm facing issue in my current project so created this question im unable to get same bloc state in other widget i tried this https://github.com/felangel/bloc/issues/74#issuecomment-457968962 but i'm getting BlocProvider.of() called with a context that does not contain a Bloc of type CounterBloc. error if add Provider again in other widget another state is created for that page how to use same bloc state in different widgets. import 'dart:async'; import 'package:flutter/material.dart'; import

问题 I'm working with a deeply nested state object in React. My code base dictates that we try to stick with function components and so every time I want to update a key/value pair inside that nested object, I have to use a hook to set the state. I can't seem to get at the deeper nested items, though. I have a drop down menu w/ an onChange handler. . .inside the onChange handler is an inline function to directly setValue of whatever key/val pair is changing. The syntax I'm using after the spread

问题 I have a problem and I'm not sure what's causing the problem. So I have done a fetch with an external api and I want to print out some of the information from the api. I have logged the data and the state variable to see if they return the data. My problem is that I don't get any data from the state variable in the console. When I log it in the console it only shows an empty array. But I get the data in the console when I'm logging console.log(data). When I remove the empty array at the end

问题 I was looking into quite a few pages to learn how to best implement an app wide bloc (for authentication, user management and initialization). I did not find so much and for a beginner regarding this level of bloc patterns I found it hard to identify a reasonable one. The pattern by Didier Boelens explained here appears to be the most promising one. Is it still a sound pattern (it is from 2018) or did the bloc library evolve in the meantime or did other patterns proved better/easier? What

问题 I was looking into quite a few pages to learn how to best implement an app wide bloc (for authentication, user management and initialization). I did not find so much and for a beginner regarding this level of bloc patterns I found it hard to identify a reasonable one. The pattern by Didier Boelens explained here appears to be the most promising one. Is it still a sound pattern (it is from 2018) or did the bloc library evolve in the meantime or did other patterns proved better/easier? What

问题 I am trying to get the text value from a dropdown select using [useState} in React Hooks. I just get the value (number) rather than the text. Ive copied the bits of code below which control the select dropdown. What am i missing here? Thanks. const [addrtype, setAddrType] = useState('Home') function handleAddrTypeChange(e) { setAddrType(e.target.value); console.log(addrtype) } <select defaultValue={addrtype} onChange={handleAddrTypeChange} className="browser-default custom-select"> <option

问题 I am trying to get the text value from a dropdown select using [useState} in React Hooks. I just get the value (number) rather than the text. Ive copied the bits of code below which control the select dropdown. What am i missing here? Thanks. const [addrtype, setAddrType] = useState('Home') function handleAddrTypeChange(e) { setAddrType(e.target.value); console.log(addrtype) } <select defaultValue={addrtype} onChange={handleAddrTypeChange} className="browser-default custom-select"> <option

问题 I'm really struggling to reset the state back to it's orginal from with a method in React. My current reset method only resets the value. I have tried adding in const equal to the original state and then setting state equal to that, but I have had no luck. Any advice? class App extends Component { state = { counters: [ { id: 1, value: 4 }, { id: 2, value: 0 }, { id: 3, value: 0 }, { id: 4, value: 0 } ] }; handleReset = () => { const counters = this.state.counters.map(c => { c.value = 0;