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[[oktatas:web:angular:angular_filter|< Angular filter]]

====== Angular PipeTransform ======

  * **Szerző:** Sallai András
  * Copyright (c) 2022, Sallai András
  * Szerkesztve: 2022, 2025
  * Licenc: [[https://creativecommons.org/licenses/by-sa/4.0/|CC Attribution-Share Alike 4.0 International]]
  * Web: https://szit.hu

===== Kezdés =====

Projekt létrehozása:
  ng new app01

Komponens létrehozása:
  ng generate component employees

Röviden:
  ng g c employees

===== Angular 17 és utána =====

==== FormsModule ====

<code javascript src/app/employee/employee.compoent.html>
import { FormsModule } from '@angular/forms';
//...
imports: [FormsModule],
</code>

==== Pipe generálása ====

A pipe generálása megegyezik az Angular 16 előtt és utána.

  ng genereate pipe shared/pipe/empfilter

Rövidítve:
  ng g p shared/pipe/empfilter


==== Ezt kapjuk ====

<code javascript src/app/shared/pipe/empfilter.pipe.ts>
import { Pipe, PipeTransform } from '@angular/core';

@Pipe({
  name: 'empfilter',
  standalone: true
})
export class EmpfilterPipe implements PipeTransform {

  transform(value: unknown, ...args: unknown[]): unknown {
    return null;
  }

}

</code>

==== A pipe ====

<code javascript src/app/shared/pipe/empfilter.pipe.ts>
import { Pipe, PipeTransform } from '@angular/core';

@Pipe({
  name: 'empfilter',
  standalone: true
})
export class EmpfilterPipe implements PipeTransform {

  transform(values: any[], filter: String): any {
    if (!values || !filter) {
      return values;
    }
    return values.filter(value => 
      value.city.toLowerCase()
      .includes(filter.toLowerCase()));
  }

}

</code>

==== Használat ====

TypeScript fájl:

<code javascript src/app/employee/employee.component.html>
import { Component } from '@angular/core';
import { EmpfilterPipe } from '../shared/pipe/empfilter.pipe';
import { FormsModule } from '@angular/forms';

@Component({
  selector: 'app-employee',
  standalone: true,
  imports: [EmpfilterPipe, FormsModule],
  templateUrl: './employee.component.html',
  styleUrl: './employee.component.css'
})
export class EmployeeComponent {

  actCity !: string;

  employees = [
    {id: 1, name: "Peres Béla", city: "Pécs", salary:395 },
    {id: 2, name: "Energia Árpád", city: "Szeged", salary: 397 },
    {id: 3, name: "Gyenge Valér", city: "Miskolc", salary: 398 },
    {id: 4, name: "Pásztó László", city: "Pécs", salary: 399 },
    {id: 5, name: "Trombita Béla", city: "Debrecen", salary: 400 },
    {id: 6, name: "Rendes Lajos", city: "Szeged", salary: 401 },
 
  ];

}

</code>


Importálni kell az EmpfilterPipe-t.

<code javascript src/app/employee/employee.compoent.html>
import { EmpfilterPipe } from '../shared/pipe/empfilter.pipe';
//...
imports: [EmpfilterPipe, FormsModule],
</code>


Az src/app/employee/employee.component.html részlete:

<code html5>
  <tbody>
    @for(emp of employees | empfilter:actCity ; track emp.id) {
      <tr>
        <td>{{emp.id}}</td>
        <td>{{emp.name}}</td>
        <td>{{emp.city}}</td>
        <td>{{emp.salary}}</td>
      </tr>
    }
  </tbody>
</code>


===== Angular 16 és korábbi verziókban =====

==== Pipe generálása ====

  ng genereate pipe shared/pipe/empfilter

Rövidítve:
  ng g p shared/pipe/empfilter


Ezt kapjuk:
<code javascript src/app/shared/pipe/empfilter.pipe.ts>
import { Pipe, PipeTransform } from '@angular/core';

@Pipe({
  name: 'empfilter'
})
export class EmpfilterPipe implements PipeTransform {

  transform(value: unknown, ...args: unknown[]): unknown {
    return null;
  }

}
</code>

Az app.module.ts fájlban vegyük fel (Az //ng g p// parancs automatikusan beteszi):
<code javascript>
  declarations: [

    EmpfilterPipe
  ],
</code>



Írjuk meg a szűrőt:

<code javascript>
  transform(values: any[], filter: Number): any {
    if (!values || !filter) {
      return values;
    }
    return values.filter(value => value.positionId == filter);
  }
</code>

==== A szűrő használata ====

<code html5>
<table>
    <tr *ngFor="let employee of employees | empfilter:actPosition ">
        <td>{{employee.id}}</td>
        <td>{{employee.name}}</td>
    </tr>
</table>
</code>
==== Teljes kód ====

<tabbox app.module.ts>

<code javascript app.module.ts>
import { NgModule } from '@angular/core';
import { FormsModule } from '@angular/forms';
import { BrowserModule } from '@angular/platform-browser';

import { AppComponent } from './app.component';
import { EmployeesComponent } from './employees/employees.component';
import { EmpfilterPipe } from './shared/pipe/empfilter.pipe';

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

</code>


<tabbox empfilter.pipe.ts>

<code javascript empfilter.pipe.ts>
import { Pipe, PipeTransform } from '@angular/core';

@Pipe({
  name: 'empfilter'
})
export class EmpfilterPipe implements PipeTransform {

  transform(values: any[], filter: Number): any {
    if (!values || !filter) {
      return values;
    }
    return values.filter(value => value.positionId == filter);
  }

}
</code>


<tabbox employees.component.ts>

<code javascript employees.component.ts>
import { Component, OnInit } from '@angular/core';

@Component({
  selector: 'app-employees',
  templateUrl: './employees.component.html',
  styleUrls: ['./employees.component.css']
})
export class EmployeesComponent implements OnInit {

  actPosition !: number;
 
  employees = [
    {"id": 1, "name": "Peres Béla", "positionId": 1},
    {"id": 2, "name": "Energia Árpád", "positionId": 1},
    {"id": 3, "name": "Gyenge Valér", "positionId": 2},
    {"id": 4, "name": "Pásztó László", "positionId": 2},
    {"id": 5, "name": "Trombita Béla", "positionId": 3},
    {"id": 6, "name": "Rendes Lajos", "positionId": 3},
 
  ];  
  constructor() { }

  ngOnInit(): void {
  }

}
</code>


<tabbox employees.component.html>

<code html employees.component.html>
<h2>Dolgozók</h2>
<input [(ngModel)]="actPosition">
<table>
    <tr *ngFor="let employee of employees | empfilter:actPosition ">
        <td>{{employee.id}}</td>
        <td>{{employee.name}}</td>
    </tr>
</table>
</code>



</tabbox>