Cannot read property 'toUpperCase' of unde

问题:

I am trying to do filter a number from a number array. but I got this errors.this a my codes.

app.module.ts

    import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { AppComponent } from './app.component';
import { NumberFilterPipe } from './number-filter.pipe';
import { FormsModule } from '@angular/forms';
import { StringFilterPipe } from './string-filter.pipe';
import { NumberFilterService } from './service/number-filter.service';


@NgModule({
  declarations: [
    AppComponent,
    NumberFilterPipe,
    StringFilterPipe
],
  imports: [
    BrowserModule,
    FormsModule
  ],
  providers: [
    NumberFilterService],
  bootstrap: [AppComponent]
})
export class AppModule { }

this the my html

<input  name= "searchtext"  [(ngModel)]="searchtext">
{{searchtext}}
<li *ngFor = "let numbers of number | number-filter : searchtext ">{{numbers}}</li>
<br><br>

this the pipe

import { Pipe, PipeTransform } from '@angular/core';
import { NumberFilterService } from './service/number-filter.service';

@Pipe({
  name: 'number-filter'
})
export class NumberFilterPipe implements PipeTransform {

flterNumber: NumberFilterService;

  transform(numbers: any, key: any): any[] {



    return this.flterNumber.filterNumber(numbers, key);


  }

}

and this the service.ts

import { Injectable } from '@angular/core';

@Injectable()
export class NumberFilterService {

    arrayLen = 0;
    itteration = 0;
    result = [];
    constructor() { }
    filterNumber(values: any[], key: any): any[] {
        this.arrayLen =  values.length;
        for (this.itteration = 0 ; this.itteration < this.arrayLen ; this.itteration ++  ) {
            if (key === values[this.itteration]) {
                this.result.push(values[this.itteration]);
            }

        }
        return this.result;
    }

}

and I got this errors.

"Uncaught Error: Template parse errors:
TypeError: Cannot read property 'toUpperCase' of undefined ("<input  name= "searchtext"  [(ngModel)]="searchtext">
{{searchtext}}
<li [ERROR ->]*ngFor = "let numbers of number | number-filter : searchtext ">{{numbers}}</li>
<br><br>"): ng:///AppModule/AppComponent.html@2:4
Parser Error: Unexpected token -, expected identifier, keyword, or string at column 31 in [let numbers of number | number-filter : searchtext ] in ng:///AppModule/AppComponent.html@2:4 ("l)]="searchtext">
{{searchtext}}
<li *ngFor = "let numbers of number | number-filter : searchtext ">[ERROR ->]{{numbers}}</li>
<br><br>"): ng:///AppModule/AppComponent.html@2:67
    at syntaxError (webpack-internal:///../../../compiler/esm5/compiler.js:684)
    at TemplateParser.parse (webpack-internal:///../../../compiler/esm5/compiler.js:24547)
    at JitCompiler._parseTemplate (webpack-internal:///../../../compiler/esm5/compiler.js:33975)
    at JitCompiler._compileTemplate (webpack-internal:///../../../compiler/esm5/compiler.js:33950)
    at eval (webpack-internal:///../../../compiler/esm5/compiler.js:33852)
    at Set.forEach (<anonymous>)
    at JitCompiler._compileComponents (webpack-internal:///../../../compiler/esm5/compiler.js:33852)
    at eval (webpack-internal:///../../../compiler/esm5/compiler.js:33722)
    at Object.then (webpack-internal:///../../../compiler/esm5/compiler.js:673)
    at JitCompiler._compileModuleAndComponents (webpack-internal:///../../../compiler/esm5/compiler.js:33721)"

I hope your valuable solution for this.thanks all . Have a nice day.

回答1:

I found this way its working

Pipe.ts

import { Pipe, PipeTransform } from "@angular/core";

@Pipe({
  name: 'myfilter'
})

export class MyFilter implements PipeTransform {
  transform(items: any[], term: any[]): any {
    if (!term)
      return items;
    return items.filter(item => item == term);
  }
}

component template

<input type="text"  [(ngModel)]="term" placeholder="filter by prefix" />
<li *ngFor="let product of listA  | myfilter:term" >{{product}}</li>

component ts

  val:number ;
  listA = [1,20,11,99];

---

Final update which is working

Below is fully tested and working

html template file

<input name="searchtext" [(ngModel)]="searchtext" (ngModelChange)="fitlerNumbers()" > {{numbers|json}}
<ul>
  <li *ngFor="let number of numbers|numberfilter:2">{{number}}</li>
</ul>

pipe.ts file

import { Pipe, PipeTransform } from '@angular/core';
import { NumberFilterService } from './NumberFilterService';

@Pipe({
  name: 'numberfilter'
})
export class NumberFilterPipe implements PipeTransform {

  constructor(public servicenum : NumberFilterService){}

  transform(numbers: any[], key: any ): any[] {
    return this.servicenum.filterNumber(numbers,key);

  }
}

Filter SErvice file

import { Injectable } from '@angular/core';

@Injectable()
export class NumberFilterService {

    arrayLen = 0;
    itteration = 0;
    result = [];
   public filterNumber(values: any[], key: any): any[] {
        this.arrayLen =  values.length;
        for (this.itteration = 0 ; this.itteration < this.arrayLen ; this.itteration ++  ) {
            if (key === values[this.itteration]) {
                this.result.push(values[this.itteration]);
            }

        }
        return this.result;
    }
}

Updates end here

回答2:

problem in below line: in your filter "number-filter" searchtext is not used but you are using in html. thats the problem try "key" instead of "searchtext" in html

<li *ngFor = "let numbers of number | number-filter : searchtext ">{{numbers}}</li>
to
<li *ngFor = "let number of numbers | number-filter : key">{{numbers}}</li>