node.js - 拒绝（TypeError）：无法读取未定义的属性“setState”，未捕获（在承诺中）类型错误：无法读取未定义的属性“setState”

Question

我有一个简单的代码，但我（有时）收到错误的结果，这是因为 NodeJS 异步，我知道。最后我需要更新“this.setState({active: options})”。所以为了解决 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相当复杂，结果也不是 100% 好。

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

请参阅简单的开始代码（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)
            }
        })

我现在正在玩这个 2 天，你有什么想法/建议吗？我找不到 setState 与 async.auto 的任何类似用法。

标签： node.jsreactjspromisesetstateasync.js

Answer 1

要解决 setState 问题，您需要注意 async.auto({}) 是一个承诺。

最后的错误函数需要删除这段代码：

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

并且在 async.auto({}) 的末尾需要添加：

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