node.js - 拒绝(TypeError):无法读取未定义的属性“setState”，未捕获( promise )TypeError:无法读取未定义的属性“setState”

我有一个简单的代码，但是我收到（有时）错误的结果，这是因为NodeJS异步，我知道。最后，我需要更新“ this.setState（{active：options}）”。因此，为了解决NodeJS的异步问题，我使用了require（“ async”）库。但是现在我的简单代码变得非常复杂，结果也不是100％令人满意。

而且在使用“ this.setState（{actove：options}）”或“ this.setState（{actove：results.optionsFill}）”的“功能之路”上，我收到错误消息：“未处理的拒绝（ TypeError）：无法读取未定义的属性'setState'和“未捕获（承诺）TypeError：无法读取未定义的属性'setState'”。

请查看简单的开始代码（该代码计算输入到地图的图例，数字周期的arr）：

    setLegend(data){

        function roundingSize(number){
        }

        function rounding(number){
        }

        function stopsArrFill(jumpLegendValue, highestNumber){
        }

        // Searching for the highestNumber POPULATION
        var highestNumber = 0

        data.features.forEach(element => {
             var value = element.properties["POPULATION"]
             if(highestNumber<value) highestNumber = value
        })

        // Need to round the number, so it will look nice on the legend
        highestNumber = roundingSize(highestNumber)

        // Searching for the LowestNumber POPULATION
        var LowestNumber = highestNumber

        data.features.forEach(element => {
            var value = element.properties["POPULATION"]
            if(LowestNumber>value) LowestNumber = value
        })

        // Need to round the number, so it will look nice on the legend
        LowestNumber = roundingSize(LowestNumber)

        // 7 because 1 element is 0 and the last is the highestNumber, so it gives 7 empty elements to fill
        var jumpLegendValue = Math.round(rounding((highestNumber - LowestNumber)/7))

        var tmpStops  = stopsArrFill(jumpLegendValue, highestNumber)

        const options = {
            name: 'Legenda',
            description: 'Liczba wystąpień',
            property: 'POPULATION',
            stops: tmpStops
        }

        this.setState({active: options})

现在，使用async.auto的复杂代码：

    setLegend(data){

        function roundingSize(number){
        }

        function rounding(number){
        }

        function stopsArrFill(jumpLegendValue, highestNumber){
        }

        async.auto({

            highestNumber: function(callback){

                // Searching for the highestNumber POPULATION
                var highestNumber = 0

                data.features.forEach(element => {
                    var value = element.properties["POPULATION"]
                    if(highestNumber<value) highestNumber = value
                })

                // Need to round the number, so it will look nice on the legend
                highestNumber = roundingSize(highestNumber)

                callback(null, highestNumber)
            },
            lowestNumber: ['highestNumber', function(results, callback){

                // Searching for the LowestNumber POPULATION
                var lowestNumber = results.highestNumber

                data.features.forEach(element => {
                    var value = element.properties["POPULATION"]
                    if(lowestNumber>value) lowestNumber = value
                })

                // Need to round the number, so it will look nice on the legend
                lowestNumber = roundingSize(lowestNumber)

                callback(null, lowestNumber)
            }],
            jumpLegendValue: ['highestNumber', 'lowestNumber', function(results, callback){

                // 7 because 1 element is 0 and the last is the highestNumber, so it gives 7 empty elements to fill
                var jumpLegendValue = Math.round(rounding((results.highestNumber - results.lowestNumber)/7))

                callback(null, jumpLegendValue)
            }],
            stopsArrFill:['highestNumber','jumpLegendValue', function(results, callback){

                // Filling the stops with jumpLegendValues
                var tmpStops  = stopsArrFill(results.jumpLegendValue, results.highestNumber)

                callback(null, tmpStops)
            }],
            optionsFill:['stopsArrFill', function(results, callback){

                const options = {
                    name: 'Legenda',
                    description: 'Liczba wystąpień',
                    property: 'POPULATION',
                    stops: results.stopsArrFill
                }

                callback(null, options)
            }],
            function (err, results)
            {
                this.setState({active:results.optionsFill})
                console.log('error: ', err)
            }
        })

我现在玩了两天，您有什么想法/建议吗？我找不到与async.auto类似的setState用法。

最佳答案

要解决setState问题，您需要意识到async.auto（{}）是一个承诺。

最后的错误功能需要删除以下代码：

function (err, results)
{
    this.setState({active:results.optionsFill})
    console.log('error: ', err)
}

在async.auto（{}）的末尾需要添加：

.then((result)=>{
    this.setState({active: result.optionsFill})
})

关于node.js - 拒绝(TypeError):无法读取未定义的属性“setState”，未捕获( promise )TypeError:无法读取未定义的属性“setState”，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/58864802/