reactJs setState更改數組內對象的屬性

Question

我再次遇到了更改數組內部對象的屬性的問題，但是這次它是數組中數組中的一個數組...

我在更改圖片預覽時遇到問題。

這沒有效果：

return {
     ...picture,
     preview: "hallo"
}

完整的代碼是：

this.setState((prevState) => ({
    stepsData: prevState.stepsData.map(step => {
        if (step.identifier === stepIdentifier) {
            console.log("lkkljk",step)

            step.onChangeContentComponents.map(
                contentComponent => {
                    if (contentComponent.pictures !== null){
                        console.log(contentComponent.pictures);
                        console.log(contentComponent.pictures[0].preview);

                        contentComponent.pictures.map(picture => {
                            return {
                                ...picture,
                                preview: "hallo"
                            }
                        });
                    }
                    return contentComponent
                }
            );

            return {
                ...step,
                [targetArray]: newArray,
            }
        }
        return step
    })
}), () => {
    console.log(this.state.stepsData)
});

謝謝。

Answer 1

問題是step.onChangeContentComponents.map調用的返回值未在任何地方使用。 您必須將代碼更改為

this.setState((prevState) => ({
    stepsData: prevState.stepsData.map(step => {
        if (step.identifier === stepIdentifier) {
            console.log("lkkljk",step)

            var newStep = step.onChangeContentComponents.map(
                contentComponent => {
                    if (contentComponent.pictures !== null){
                        console.log(contentComponent.pictures);
                        console.log(contentComponent.pictures[0].preview);

                        contentComponent.pictures.map(picture => {
                            return {
                                ...picture,
                                preview: "hallo"
                            }
                        });
                    }
                    return contentComponent
                }
            );

            return newStep
        }
        return step
    })
}), () => {
    console.log(this.state.stepsData)
});

但是我建議您不要在setState中進行復雜的計算，而應該像這樣在外部抽象計算

var stepsData = [...this.state.stepsData];
stepsData = stepsData.map(step => {
        if (step.identifier === stepIdentifier) {

            var newStep = step.onChangeContentComponents.map(
                contentComponent => {
                    if (contentComponent.pictures !== null){
                        console.log(contentComponent.pictures);
                        console.log(contentComponent.pictures[0].preview);

                        contentComponent.pictures.map(picture => {
                            return {
                                ...picture,
                                preview: "hallo"
                            }
                        });
                    }
                    return contentComponent
                }
            );

            return newStep
        }
        return step
     });

this.setState({stepsData}, () => {
    console.log(this.state.stepsData)
});

Answer 2

嘗試使用immutability-helper util來解決它。

之前，該實用程序已包含在react-addons-update模塊中。

Answer 3

解決方案可能是

let stepsData = [...this.state.stepsData];
    stepsData = stepsData.map(step => {
        if (step.identifier === stepIdentifier) {
            return {
                ...step,
                [targetArray]: newArray,
                onChangeContentComponents: step.onChangeContentComponents.map(contentComponent => {
                        if (contentComponent.pictures !== null) {
                            return {
                                ...contentComponent,
                                pictures: contentComponent.pictures.map(picture => {
                                    console.log(picture)
                                    return {
                                        ...picture,
                                        preview: "hallo"
                                    }
                                })
                            }
                        }
                        return contentComponent
                    }
                )
            }
        }
        return step
    });
    this.setState({stepsData: stepsData}, () => {
        console.log(this.state.stepsData)
    });