state

问题 I come from a React background but I'm switching to Svelte and Sapper for my next application in order to fight the massive bundle size that comes with React these days. However, I'm having trouble initializing Svelte's store with data retreived from localStorage. As per the Sapper docs (https://sapper.svelte.dev/docs#Getting_started), I created my project by running npx degit "sveltejs/sapper-template#rollup" my-app from the command line. I then installed the dependencies and removed the

问题 When i'm clicking submit button it requires to clicks to properly fire off the function. I didn't have problem before implementing if statements. Does it have something with fact that i have 2 if statements inside and after each click it checks only 1 if statement? onSubmit = (e) => { const { firstName, lastName, email, eventDate, validation} = this.state if (firstName, lastName, eventDate, email) { this.setState({validation: true}) if (new RegExp(/[a-z0-9._%+-]+@[a-z0-9.-]+\.[a-z]{2,15}/g)

问题 I am building a react app. I have created a dynamic form (generates X number of input fields (1-10) based on the number chosen by the user).That part works perfectly. However, I am wanting to add a second input field inside my mapping function. For context, I am building a flash card app. I want to add the term and the definition to the same state item. The idea is that each state array will hold an object for the term and an object for the definition in order to keep each definition with its

问题 The class StatelessWidget is marked as immutable . However, I am using the scoped model , which means that I avoid StatefulWidget and use the model to alter state in StatelessWidget . This leads to me having non-final fields in StatelessWidget , which doesn't cause errors , because it's just a warning . But I wondered if there is a better way? 回答1: Stateless widgets should only have final fields, with no exceptions . Reason: When the parent widget is rebuilt for some reason (screen rotation,

问题 I have two textfields, assigned to: @State private var emailAddress: String = "" @State private var password: String = "" Now whenever I am typing on it, the app seems to get stuck and gives me this error: 'Modifying state during view update, this will cause undefined behavior.' I have a StartView() : class UserSettings: ObservableObject { var didChange = PassthroughSubject<Void, Never>() @Published var loggedIn : Bool = false { didSet { didChange.send(()) } } } struct StartView: View {

问题 I have two textfields, assigned to: @State private var emailAddress: String = "" @State private var password: String = "" Now whenever I am typing on it, the app seems to get stuck and gives me this error: 'Modifying state during view update, this will cause undefined behavior.' I have a StartView() : class UserSettings: ObservableObject { var didChange = PassthroughSubject<Void, Never>() @Published var loggedIn : Bool = false { didSet { didChange.send(()) } } } struct StartView: View {

问题 I have two textfields, assigned to: @State private var emailAddress: String = "" @State private var password: String = "" Now whenever I am typing on it, the app seems to get stuck and gives me this error: 'Modifying state during view update, this will cause undefined behavior.' I have a StartView() : class UserSettings: ObservableObject { var didChange = PassthroughSubject<Void, Never>() @Published var loggedIn : Bool = false { didSet { didChange.send(()) } } } struct StartView: View {

问题 I have a bootstrap grid where each grid item is populated from an array of objects but after each grid item I would like to have a vote button. How could I achieve this with maintaining state on each button separately, ie when button 1 is clicked the text should change from 'vote' to 'voted' whilst the others remain as 'vote'. At the moment when a button is clicked, all of them change to 'Voted' class Items extends Component { constructor(props) { super(props); this.state = { hasVoted: false

问题 I have a multi-step form that I want to implement in React using Formik , Material-ui , functional components, and the getState hook. import React, { useState, Fragment } from 'react'; import { Button, Stepper, Step, StepLabel } from '@material-ui/core'; import FormPartA from './FormPartA'; import FormPartB from './FormPartB'; import FormPartC from './FormPartC'; function MultiStepForm(props) { const steps = ['Part A', 'Part B', 'Part C']; const passedValues = props.values || {}; const

问题 In the login view, if the user taps on the login button without having inserted his credentials, the LoginFailState is yield and the view reacts to it. If he taps again, this LoginFailstate is yield again, but the view doesn't react to it. So, is there a way to yield more times the same state? There is some code to better explain my situation: class LoginBloc extends Bloc<LoginEvent, LoginState> { @override LoginState get initialState => LoginUninitialized(); @override Stream<LoginState>