无法使用“findIndex”函数访问类变量 - 已解决

Question

我无法从findIndex方法访问我的类变量。 My whole class:    import { Component, Input, OnInit } from '@angular/core';import { History } from '../model/history';import { SharedService } from "../shared.service";@Component({  selector: 'app-details',  templateUrl: './details.component.html',  styleUrls: ['./details.component.scss']})export class DetailsComponent implements OnInit {  history: History[] = [    {      basic_text: { basic_text: 'text_1' },      summary: { summary: 'summary_1' },      tager: { tag_algorytm: true, tag_text: "tag_1" }    },    {      basic_text: { basic_text: 'text_2' },      summary: { summary: 'summary_2' },      tager: { tag_algorytm: false, tag_text: "tag_2" }    }  ];  basic_text: String = "Tekst podstawowy";  summary: String = "Streszczenie";  rating: String = "Ocenione zdania";  chosedText: string;  asd: string = 'asdad';  constructor(private sharedService: SharedService) { }  ngOnInit() {    this.sharedService.sharedMessage.subscribe(chosedText => this.chosedText = chosedText)  }  textFilter(h: History[]) {    let result: History[] = [];    var param = this.chosedText;    var foundIndex = h.findIndex(this.isEqualToSelectedText, param);    result.push(h[foundIndex])    return result;  }  // The function was moved out  private isEqualToSelectedText(element: History) {    return element.basic_text.basic_text === this.chosedText;  }}但如果我这样做var x= h.findIndex(isEqualToSelectedText, 'text_1');一切正常。我尝试从 isEqualToSelectedText 函数访问我的类 varialb 。但我总是遇到这个错误。在findIndex运行期间，单词“this”应等于“text_1”。你能帮助我吗？

Answer 1

this由于函数作用域的原因，将失去其引用。您可以使用箭头函数，这样它就可以保留其范围，甚至可以将该isEqualToSelectedText函数移出该类中的私有方法。

它可能是这样的：

// in the same place you're declaring the function

const isEqualToSelectedText = (element : History) => {

      return element.basic_text.basic_text === this.chosedText;

}

// or moving out to a private method in the class

export class DetailsComponent implements OnInit {

    history: History[] = [

        {

            basic_text: { basic_text : 'text_1' },

            summary: { summary : 'summary_1' },

            tager: { tag_algorytm : true, tag_text: 'tag_1' }

        },

        {

            basic_text: { basic_text : 'text_2' },

            summary: { summary : 'summary_2' },

            tager: { tag_algorytm : false, tag_text: 'tag_2' }

        }

    ];

    chosedText: string = 'text_1';

    textFilter(h: History[]) {

        let result: History[] = [];

        var param = this.chosedText;

        var foundIndex= h.findIndex(this.isEqualToSelectedText, param); // <-- changing here

        result.push(h[foundIndex])

        return result;

    }

    // The function was moved out

    private isEqualToSelectedText(element: History) {

        return element.basic_text.basic_text === this.chosedText;

    }

}

Answer 2

好的，我已经找到错误了。我在使用“http get”初始化变量之前使用了它。所以问题已经解决了，感谢帮助。