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/*
* Copyright (c) 2022. Deutsche Telekom AG
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* SPDX-License-Identifier: Apache-2.0
*/
import { Pipe, PipeTransform } from '@angular/core';
@Pipe({
name: 'map',
pure: false
})
/*
MapPipe allows us to run a function in a template
for example, you need to filter out some elements from the array before displaying these elements. You can call a function for getting filtered array
directly from template, but this function will be triggered everytime when user interacts with page.
MapPipe allows you to call a function through this pipe, so function will be called only when necessary.
Usage:
we have function in .ts file that's called filterZeroValues
in template we can use this function:
*ngFor="let item in elements | map : filterZeroValues"
where the first parameter of map pipe is function to be called, and other parameters will be passed as arguments to this function
Important note: as you can see from implementation, elements array will be passed to your function as a first argument
*/
export class MapPipe implements PipeTransform {
transform<T, R>(
thisArg: T,
project: (t:T, ...others: any[]) => R,
...args: any[]
): R {
return project(thisArg, ...args);
}
}
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