Checks if this is the default write concern

# MongoDB\Driver\WriteConcern::isDefault

(mongodb >=1.3.0)

MongoDB\Driver\WriteConcern::isDefault — Checks if this is the default write concern

### 説明

final public MongoDB\Driver\WriteConcern::isDefault ( void ) : bool

Returns whether this is the default write concern (i.e. no options are specified). This method is primarily intended to be used in conjunction with MongoDB\Driver\Manager::getWriteConcern() to determine whether the Manager has been constructed without any write concern options.

The driver will not include a default write concern in its write operations (e.g. MongoDB\Driver\Manager::executeBulkWrite()) in order to allow the server to apply its own default, which may have been » modified. Libraries that access the Manager's write concern to include it in their own write commands should use this method to ensure that default write concerns are left unset.

### パラメータ

この関数にはパラメータはありません。

### 返り値

Returns `TRUE` if this is the default write concern and `FALSE` otherwise.

### エラー / 例外

- 引数のパースに失敗した場合に MongoDB\Driver\Exception\InvalidArgumentException をスローします。

### 例

例1 MongoDB\Driver\WriteConcern::isDefault() example

`<?php
$wc = new MongoDB\Driver\WriteConcern(1);
var_dump($wc->isDefault());
$manager = new MongoDB\Driver\Manager('mongodb://127.0.0.1/?w=majority');
$wc = $manager->getWriteConcern();
var_dump($wc->isDefault());
$manager = new MongoDB\Driver\Manager('mongodb://127.0.0.1/');
$wc = $manager->getWriteConcern();
var_dump($wc->isDefault());
?>`

上の例の出力は以下となります。

    bool(false)
    bool(false)
    bool(true)

### 参考

- MongoDB\Driver\Manager::getWriteConcern() - Return the WriteConcern for the Manager
- » Modify Default Write Concern in the MongoDB manual
- » Write Concern reference