反应上下文:TypeError:渲染不是函数 [英] React Context: TypeError: render is not a function

问题描述

我正在尝试使用React Context将函数传递给嵌套的子组件，这样可以有效地使孩子在按下时更新父状态.

I'm trying to use React Context to pass a function to a nested child component, which effectively allows the child to update the parents state when pressed.

问题是我似乎收到错误'TypeError:render不是函数.(在render(newValue)中，render是Array的一个实例.，并且控制台中的错误显示为:警告:上下文使用者使用多个子对象或不是功能的子对象进行渲染)上下文使用者需要一个作为功能的子代.如果您确实传递了一个功能，请确保该功能周围没有尾随或前导空格.'

The problem is I seem to be getting an error 'TypeError: render is not a function. (In render(newValue), render is an instance of Array' and an error in my console reads: 'Warning: A context consumer was rendered with multiple children, or a child that isn't a function. A context consumer expects a single child that is a function. If you did pass a function, make sure there is no trailing or leading whitespace around it.'

我已经查看了这个错误以及文档，但是似乎没有答案可以回答我的问题，我无法弄清楚为什么它不起作用.

I've looked around at this error and also at documentation but no answers seem to answer my question, I can't quite work out why this isn't working.

编辑:我应该补充一点，因为它们是根据对象数组构建的，因此呈现了多个子组件

I should add that there are multiple child components rendered, as they're built from an array of objects

摘要:

父母:

class Product extends Component {
    state = {
        selected_ind: 0
    };

    handleContextChange = selected_ind => {
        this.setState({selected_ind});
    };

    render() {
        const contextValue = {
            data: this.state,
            handleChange: this.handleContextChange
        };

        //Desconstruct props for ease of use
        const {
            attr_data,
            variant,
            product_name } = this.props;


        return (
                <Container>
                    <Heading>Product Options</Heading>
                    <IndexContext.Provider value={contextValue}>
                        <OptionTile
                            tileColor='grey'
                            onPress={ () => this.props.navigation.navigate('Variants', {
                                attr_data: attr_data,
                                selected_ind: this.state.selected_ind
                            })} //Replace with named function
                            option="Variant"
                            selected_ind={ this.state.selected_ind }
                            value={ selected_attr.name } />
                    </IndexContext.Provider>
                    <OptionTile
                        tileColor='grey'
                        option="Quantity"
                        value="1" />
                </Container>

在OptionTile中是我要在其中使用该功能的孩子:

Within OptionTile is the child I'd like to use the function within:

const VariantTile = (props) => {
    return (
        <IndexContext.Consumer>
            {({ handleChange }) => (
                <TouchableOpacity onPress={handleChange(props.index)}>
                    <AsyncImage
                        source={ props.img_src }
                        placeholderColor="#fafafa"
                        style={{ flex: 1, width: null, height: 200 }}
                    />
                    <Text>{ props.var_name }</Text>
                    <Text>{ props.price }</Text>
                    <Text>{ props.sku }</Text>
                </TouchableOpacity>
            )};
        </IndexContext.Consumer>
    )
};

上下文组件很简单:

const IndexContext = React.createContext();

export default IndexContext;

推荐答案

由于错误状态，< Consumer> 应该是唯一的孩子，并且应该是一个函数.当它有多个子节点(包括文本节点)时，会出现该错误.

As the error states, <Consumer> should have the only child, and it should be a function. The error appears when it has multiple children, including text nodes.

; 会导致问题.它不是表达式的一部分，使其成为表达式的一部分会导致语法错误.

; after embedded expression causes the problem. It's not a part of an expression, and making it a part of it would result in syntax error.

应该是:

<IndexContext.Consumer>
    {({ handleChange }) => (
        <TouchableOpacity onPress={handleChange(props.index)}>
            <AsyncImage
                source={ props.img_src }
                placeholderColor="#fafafa"
                style={{ flex: 1, width: null, height: 200 }}
            />
            <Text>{ props.var_name }</Text>
            <Text>{ props.price }</Text>
            <Text>{ props.sku }</Text>
        </TouchableOpacity>
    )}
</IndexContext.Consumer>

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