我正在开发一些反应原生的类,这就出现了:
class Foo extends Component {
constructor(props) {
super(props)
this.state = {
days: [{text: 'Sofort', id: 1, selected: true}, {text: 'Morgen', id: 2, selected: false}, {text: 'Montag', id: 3, selected: false}, {text: 'Samstag', id: 4, selected: false}, {text: 'Sonntag', id: 5, selected: false}]
}
}
onDaySelection(selectedDay) {
// some logic to change the selected day
}
render() {
<Bar data={this.state.days} callback={this.onDaySelection(selectedDay)}>
}
}
酒吧班:
class Bar extends Component {
constructor(props) {
super(props)
let dataSource = new ListView.DataSource(
{rowHasChanged: (r1, r2) => r1.id !== r2.id}
)
this.state = {
dataSource: dataSource.cloneWithRows(this.props.days),
}
}
componentWillReceiveProps(newProps) {
let dataSource = new ListView.DataSource(
{rowHasChanged: (r1, r2) => r1.id !== r2.id}
)
this.state = {
dataSource: dataSource.cloneWithRows(newProps.days),
}
}
renderRow(rowData) {
let tick = rowData.selected? (
<Image source={require('../assets/images/Checkbox.png')}/>
): (
<Image source={require('../assets/images/CheckboxEmpty.png')}/>
)
return (
<View>
<TouchableOpacity
onPress={ () => {this.props.callback(rowData)}}
style={appStyles.flowRight}
>
{tick}
<Text>{rowData.text}</Text>
</TouchableOpacity>
</View>
)
}
render() {
return (
<ListView
dataSource={this.state.dataSource}
renderRow={this.renderRow.bind(this)}
/>
)
}
}
正如您所看到的,我必须在Bar类上实现方法componentWillReceiveProps,为什么会这样?为什么没有再次调用构造函数,是因为存储没有被更新?这是一个正确的模式吗?
编辑:似乎我的问题不明确,因为有其他组件接收道具,只有一个构造函数,并在其道具更新时相应更新,例如:class CustomCarouselIndicator extends Component {
constructor(props) {
super(props)
}
render() {
let indicatorArray = []
for(let i = 0; i < this.props.length; i++) {
indicatorArray.push(i)
}
let indicators = indicatorArray.map(index => {
let isSelected = index == this.props.selected
//Some more logic
})
return (
<View style={[appStyles.flowRight, {flex: 1, justifyContent: 'center', alignItems:'center'}, this.props.style]}>
{indicators}
</View>
)
}
}
每当我更改选定的道具时,组件都会更新,无需实现componentWillReceiveProps。
这两个类都在我的代码库中使用,但在一个我必须实现将接收道具方法,另一方面我没有做任何事情来让组件在传递给它的新道具时更新。
答案 0 :(得分:6)
构造函数只调用一次。每当道具更新时,都会调用componentWillReceiveProps;这是这种逻辑的正确位置。