# WHMCS\UsageBilling\Contracts\Metrics\MetricInterface

`Interface`

MetricInterface

## Constants

| Name | Description |
|  --- | --- |
| `TYPE_SNAPSHOT` |  |
| `TYPE_PERIOD_DAY` |  |
| `TYPE_PERIOD_MONTH` |  |


## Methods

### usage

```php
public function usage()
```

**Returns** `UsageInterface`

### withUsage

```php
public function withUsage(UsageInterface $usage = null)
```

### units

```php
public function units()
```

**Returns** `UnitInterface;`

### systemName

```php
public function systemName()
```

Canonical name to be used by code and between systems

**Returns** `string`

### displayName

```php
public function displayName()
```

Name to render in UI to users

**Returns** `string`

### type

```php
public function type()
```

One of the TYPE_* constants of this instance

**Returns** `string`