无法访问 "findIndex" 函数内的 class 变量 - 已解决

Question

我无法通过 findIndex 方法访问我的 class 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;
  }

}

我正在为 thisArg 分配值 chosedText。我遇到的错误：

core.js:5967 ERROR TypeError: Cannot read property 'basic_text' of undefined
    at DetailsComponent_tr_12_Template (details.component.html:11)
    at executeTemplate (core.js:9274)
    at refreshView (core.js:9143)
    at refreshEmbeddedViews (core.js:10263)
    at refreshView (core.js:9167)
    at refreshComponent (core.js:10309)
    at refreshChildComponents (core.js:8940)
    at refreshView (core.js:9193)
    at refreshComponent (core.js:10309)
    at refreshChildComponents (core.js:8940)

但如果我这样做

var x= h.findIndex(isEqualToSelectedText, 'text_1');

一切正常。我试图从 isEqualToSelectedText 函数访问我的 class varialb。但我总是遇到这个错误。在 findIndex 的运行期间，单词“this”应该等于 'text_1'。你能帮帮我吗？

Answer 1

this 会因为函数作用域而失去它的引用。您可以使用箭头函数，以便它可以保留其范围，甚至可以将 isEqualToSelectedText 函数移出到 class.

中的私有方法

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，我找到错误了。在“http get”初始化之前，我正在使用我的变量。至此问题解决，感谢帮助

无法访问 "findIndex" 函数内的 class 变量 - 已解决

Cannot access class varaible withing "findIndex" function - resolved

javascript

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typescript