79 lines
2.6 KiB
TypeScript
79 lines
2.6 KiB
TypeScript
import {Injectable, PipeTransform, WrappedValue, Pipe} from '@angular/core';
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import {isBlank, isString, isArray, StringWrapper} from '../../src/facade/lang';
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import {BaseException} from '../../src/facade/exceptions';
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import {ListWrapper} from '../../src/facade/collection';
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import {InvalidPipeArgumentException} from './invalid_pipe_argument_exception';
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/**
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* Creates a new List or String containing only a subset (slice) of the
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* elements.
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*
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* The starting index of the subset to return is specified by the `start` parameter.
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*
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* The ending index of the subset to return is specified by the optional `end` parameter.
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*
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* ### Usage
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*
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* expression | slice:start[:end]
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*
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* All behavior is based on the expected behavior of the JavaScript API
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* Array.prototype.slice() and String.prototype.slice()
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*
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* Where the input expression is a [List] or [String], and `start` is:
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*
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* - **a positive integer**: return the item at _start_ index and all items after
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* in the list or string expression.
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* - **a negative integer**: return the item at _start_ index from the end and all items after
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* in the list or string expression.
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* - **`|start|` greater than the size of the expression**: return an empty list or string.
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* - **`|start|` negative greater than the size of the expression**: return entire list or
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* string expression.
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*
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* and where `end` is:
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*
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* - **omitted**: return all items until the end of the input
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* - **a positive integer**: return all items before _end_ index of the list or string
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* expression.
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* - **a negative integer**: return all items before _end_ index from the end of the list
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* or string expression.
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*
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* When operating on a [List], the returned list is always a copy even when all
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* the elements are being returned.
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*
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* When operating on a blank value, returns it.
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*
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* ## List Example
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*
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* This `ngFor` example:
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*
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* {@example core/pipes/ts/slice_pipe/slice_pipe_example.ts region='SlicePipe_list'}
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*
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* produces the following:
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*
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* <li>b</li>
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* <li>c</li>
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*
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* ## String Examples
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*
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* {@example core/pipes/ts/slice_pipe/slice_pipe_example.ts region='SlicePipe_string'}
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*/
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@Pipe({name: 'slice', pure: false})
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@Injectable()
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export class SlicePipe implements PipeTransform {
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transform(value: any, start: number, end: number = null): any {
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if (isBlank(value)) return value;
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if (!this.supports(value)) {
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throw new InvalidPipeArgumentException(SlicePipe, value);
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}
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if (isString(value)) {
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return StringWrapper.slice(value, start, end);
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}
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return ListWrapper.slice(value, start, end);
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}
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private supports(obj: any): boolean { return isString(obj) || isArray(obj); }
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}
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