# MongoDB\Driver\WriteConcern::isDefault

(mongodb >=1.3.0)

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

### 说明

final public MongoDB\Driver\WriteConcern::isDefault(): 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.

### 参数

此函数没有参数。

### 返回值

Returns `true` if this is the default write concern and `false` otherwise.

### 错误／异常

- Throws MongoDB\Driver\Exception\InvalidArgumentException on argument parsing errors.

### 示例

示例 #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());
?>`

以上示例会输出：

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

### 参见

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

`↑` and `↓` to navigate • `Enter` to select • `Esc` to close • `/` to open