Question

有什么方法可以检查 array_filter 是否从数组中删除了任何值？

我想到的解决方案是这些：

$sample_array = ["values"];
$array_copy = $sample_array;

if (array_filter($sample_array, 'fn') === $array_copy) {
    #Some value was deleted from the array
} else {
    #The array was not modified
}

这似乎效率不高，因为它必须复制整个数组。

$sample_array = ["values"];
$array_count = count($sample_array);

if (count(array_filter($sample_array, 'fn')) === $array_count) {
    #The array was not modified
} else {
    #Some value was deleted from the array
}

这似乎更有效率，尽管我想知道是否有更优雅的方式来解决这个问题。

预先感谢您。

Answer 1

您可以扩展功能以跟踪更改本身。

if __name__ == '__main__':
    app.run()

将function ianreadfile (csName,arrayno,callback){ var tArray = new Array(); Papa.parse(csName,{ delimiter: "", newline: "", download: true, complete: function(results){ var data = results.data; for(var i=0;i<data.length;i++){ var row = data[i]; tArray.push(row); } implement(arrayno); }//end complete }); callback(); } function finished(){ alert("in finished"); var ian1="QQQQW"; } ianreadfile (csName,arrayno,finished);返回为2。

Answer 2

使用array_diff比较两个数组。

if(array_diff($array_copy, $sample_array))
    echo "not same";

Answer 3

使用'count（）'是恕我直言，这是最优雅的解决方案，我怀疑这可能会效率更高-您需要对其进行度量。 OTOH，供您考虑...

 function fn($arg, $mode='default')
 {
     static $matched;

     if ('default'==$mode) {
        $result=real_filter_fn($arg);
        $matched+=$result ? 1 : 0;
        return $result;
     }
     $result=$matched;
     $matched=0;
     return $result;
 }

Answer 4

您可以使用闭包来更改布尔变量的状态：

$sample_array = [1,2,3,4];
$array_changed = false;

//Use closure to change $array_changed
print_r(array_filter($sample_array, function($var) use (&$array_changed) {
    $check = (!($var & 1));
    $array_changed = $array_changed?:$check;
    return $check;
}));

if ($array_changed) {
    #Some value was deleted from the array
} else {
    #The array was not modified
}

[编辑]

与我的相比，这是您的解决方案的简单速度测试：

/**********************SPEEDTEST**************************/

function fn ($var) {
    return (!($var & 1));
}
$sample_array = [1,2,3,4];

$before = microtime(true);

for ($i=0 ; $i<100000 ; $i++) {

    $array_changed = false;

    //Use closure to change $array_changed
    array_filter($sample_array, function($var) use (&$array_changed) {
        $check = (!($var & 1));
        $array_changed = $array_changed?:$check;
        return $check;
    });
    if ($array_changed) {
        #Some value was deleted from the array
    } else {
        #The array was not modified
    }

}

$after = microtime(true);
echo "Using closure:      " . ($after-$before)/$i . " sec/run\n";

echo '<br>';
/*******************************************************/

$before = microtime(true);

for ($i=0 ; $i<100000 ; $i++) {

    $array_copy = $sample_array;

    if (array_filter($sample_array, 'fn') === $array_copy) {
        #Some value was deleted from the array
    } else {
        #The array was not modified
    }

}

$after = microtime(true);
echo "Using array copy:    " . ($after-$before)/$i . " sec/run\n";

echo '<br>';
/*******************************************************/

$before = microtime(true);

for ($i=0 ; $i<100000 ; $i++) {

    $array_count = count($sample_array);

    if (count(array_filter($sample_array, 'fn')) === $array_count) {
        #The array was not modified
    } else {
        #Some value was deleted from the array
    }

}

$after = microtime(true);
echo "Using array count:   " . ($after-$before)/$i . " sec/run\n";

结果：

Using closure:       9.1402053833008E-7 sec/run
Using array copy:    4.9885988235474E-7 sec/run
Using array count:   5.5881977081299E-7 sec/run

也许有助于决策：）

Answer 5

如果要跟踪已删除的元素，可以执行以下操作。

$sample_array = ['values', 'test'];
$removed = []; // Contains all the removed values.

$new_array = array_filter($sample_array, function($value) use (&$removed) {
    if($value == 'test') {
        $removed[] = $value; // Adds the value to the removed array.
        return false;
    }

    return true;
});

print_r($removed);

PHP：检查array_filter是否从数组中删除了任何条目

5 个答案: