我试图通过函数作为道具。 我以前这样做过，但是现在使用相同的逻辑，它会给我错误（this.props.FunctionName不是一个函数）。 我有一个子组件（Navbar）和一个父组件（MainComponent）。 我想从Navbar向MainComponet发送一个输入值，并将其设置为父组件中的状态值。
父组件
import React ,{Component}from 'react'
import Navbar from '../Presentational/Navbar'
class Main extends Component{
constructor(props){
super(props)
this.state = {
searchItem: ''
}
}
GetSearchItem(search){
this.setState({searchItem:search})
}
render(){
return(
<div className = 'container'>
<div className = 'row'>
<div className = 'col-12 mt-1'>
<Navbar onChange = {(search)=>this.GetSearchItem(search)}></Navbar>
</div>
</div>
<div className = 'row'>
<div className = 'col-3'>
<h3>{this.state.searchItem}</h3>
</div>
</div>
</div>
)
}
}
export default Main
子组件（导航栏）
import React,{Component} from 'react'
import {AppBar,Toolbar,IconButton,Typography,InputBase} from '@material-ui/core'
import MenuIcon from '@material-ui/icons/Menu';
import SearchIcon from '@material-ui/icons/Search';
import {fade , makeStyles} from '@material-ui/core/styles'
const useStyles = makeStyles((theme) => ({
root: {
flexGrow: 1,
},
menuButton: {
marginRight: theme.spacing(2),
},
title: {
flexGrow: 1,
display: 'none',
[theme.breakpoints.up('sm')]: {
display: 'block',
},
},
search: {
position: 'relative',
borderRadius: theme.shape.borderRadius,
backgroundColor: fade(theme.palette.common.white, 0.15),
'&:hover': {
backgroundColor: fade(theme.palette.common.white, 0.25),
},
marginLeft: 0,
width: '100%',
[theme.breakpoints.up('sm')]: {
marginLeft: theme.spacing(1),
width: 'auto',
},
},
searchIcon: {
padding: theme.spacing(0, 2),
height: '100%',
position: 'absolute',
pointerEvents: 'none',
display: 'flex',
alignItems: 'center',
justifyContent: 'center',
},
inputRoot: {
color: 'inherit',
},
inputInput: {
padding: theme.spacing(1, 1, 1, 0),
// vertical padding + font size from searchIcon
paddingLeft: `calc(1em + ${theme.spacing(4)}px)`,
transition: theme.transitions.create('width'),
width: '100%',
[theme.breakpoints.up('sm')]: {
width: '12ch',
'&:focus': {
width: '20ch',
},
},
},
}));
class Navbar extends Component{
render(){
const classes = this.props.classes;;
return(
<div className={classes.root}>
<AppBar position="static">
<Toolbar>
<IconButton
edge="start"
className={classes.menuButton}
color="inherit"
aria-label="open drawer"
>
<MenuIcon />
</IconButton>
<Typography className={classes.title} variant="h6" noWrap>
Pizaa Valley
</Typography>
<div className={classes.search}>
<div className={classes.searchIcon}>
<SearchIcon />
</div>
<InputBase
placeholder="Search…"
classes={{
root: classes.inputRoot,
input: classes.inputInput,
}}
inputProps={{ 'aria-label': 'search' }}
onChange={(event)=>this.props.onChange(event.target.value)}
/>
</div>
</Toolbar>
</AppBar>
</div>
)
}
}
export default () => {
const classes = useStyles();
return (
<Navbar classes={classes} />
)
}
您已经正确地完成了所有操作，只是更改了以下内容:
GetSearchItem(search){
this.setState({searchItem:search})
}
至
GetSearchItem = (search) => {
this.setState({searchItem:search})
}
作为箭头函数，它可以访问上面的作用域
问题是您有两种navbar类型。 您有使用class navbar创建的类组件，您有下面的功能组件，代码如下。
export default () => {
const classes = useStyles();
return (
<Navbar classes={classes} />
)
}
当你做的时候
从“../presentation/Navbar”
onChange属性被提供给功能组件，但从不传递给基于类的组件。 您可以通过以下代码替换您的功能组件来修复此问题:
export default props => {
const classes = useStyles();
return (
// using the "spread operator", we pass along all the props given
// to the functional component, so the class-based component can also access
// these
<Navbar ...props classes={classes} />
)
}
