Creates a new map using a callable to determine which pairs to include

Ds\Map::filter

(PECL ds >= 1.0.0)

Ds\Map::filter Creates a new map using a callable to determine which pairs to include

說明

public Ds\Map::filter(callable $callback = ?): Ds\Map

Creates a new map using a callable to determine which pairs to include.

參數

callback

callback(mixed $key, mixed $value): bool

Optional callable which returns true if the pair should be included, false otherwise.

If a callback is not provided, only values which are true (see converting to boolean) will be included.

返回值

A new map containing all the pairs for which either the callback returned true, or all values that convert to true if a callback was not provided.

範例

示例 #1 Ds\Map::filter() example using callback function

<?php
$map 
= new \Ds\Map(["a""b""c""d""e"]);

var_dump($map->filter(function($key$value) {
    return 
$key == 0;
}));
?>

以上例程的輸出類似於:

object(Ds\Map)#3 (3) {
  [0]=>
  object(Ds\Pair)#2 (2) {
    ["key"]=>
    int(0)
    ["value"]=>
    string(1) "a"
  }
  [1]=>
  object(Ds\Pair)#4 (2) {
    ["key"]=>
    int(2)
    ["value"]=>
    string(1) "c"
  }
  [2]=>
  object(Ds\Pair)#5 (2) {
    ["key"]=>
    int(4)
    ["value"]=>
    string(1) "e"
  }
}

示例 #2 Ds\Map::filter() example without a callback function

<?php
$map 
= new \Ds\Map(["a" => 0"b" => 1"c" => true"d" => false]);

var_dump($map->filter());
?>

以上例程的輸出類似於:

object(Ds\Map)#2 (3) {
  [0]=>
  int(1)
  [1]=>
  string(1) "a"
  [2]=>
  bool(true)
}

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