`validates_numericality_of`¶

The validates_numericality_of validation in ActiveRecord allows you to validate whether an attribute's value is a valid numeric value. It ensures that the attribute contains a number and optionally checks for numerical constraints such as minimum and maximum values. To use validates_numericality_of, you need to specify the following options:

Attribute Name: This option specifies the name of the attribute you want to validate for numericality. It is typically set as a symbol or string.
```
static $validates_numericality_of = [
    'age' => []
];
```
Message (Optional): To customize the error message displayed when the validation fails, you can use the message option to provide a custom error message.
```
static $validates_numericality_of = [
    'price' => [
        'message' => 'Price must be a valid number.',
    ],
];
```
Only Integer (Optional): The only_integer option allows you to specify whether the attribute's value must be an integer. By default, only_integer is set to false, meaning that any numeric value is accepted. You can set it to true to enforce integer values.
```
static $validates_numericality_of = [
    'quantity' => [
        'only_integer' => true
    ]
];
```
Greater Than (Optional): The greater_than option allows you to specify a minimum value that the attribute's value must be greater than. It ensures that the numeric value is greater than the specified threshold.
```
static $validates_numericality_of = [
    'score' => [
        'greater_than' => 0
    ]
];
```
Greater Than Or Equal To (Optional): The greater_than_or_equal_to option allows you to specify a minimum value that the attribute's value must be greater than or equal to. It ensures that the numeric value is greater than or equal to the specified threshold.
```
static $validates_numericality_of = [
    'temperature' => [
        'greater_than_or_equal_to' => -20
    ]
];
```
Less Than (Optional): The less_than option allows you to specify a maximum value that the attribute's value must be less than. It ensures that the numeric value is less than the specified threshold.
```
static $validates_numericality_of = [
    'discount' => [
        'less_than' => 100
    ]
];
```
Less Than Or Equal To (Optional): The less_than_or_equal_to option allows you to specify a maximum value that the attribute's value must be less than or equal to. It ensures that the numeric value is less than or equal to the specified threshold.
```
static $validates_numericality_of = [
    'percentage' => [
        'less_than_or_equal_to' => 100
    ]
];
```
Equal To (Optional): The equal_to option allows you to specify a value that the attribute's value must be equal to. It ensures that the numeric value matches the specified value.
```
static $validates_numericality_of = [
    'quantity' => [
        'equal_to' => 10
    ]
];
```
Allow Blank (Optional): The allow_blank option allows you to specify whether the attribute is allowed to be empty (e.g., an empty string). By default, allow_blank is set to false, meaning that the attribute must not be blank. You can set it to true to allow blank values.
```
static $validates_numericality_of = [
    'price' => [
        'allow_blank' => true
    ]
];
```
Allow Null (Optional): The allow_null option allows you to specify whether the attribute is allowed to be null. By default, allow_nil is set to false, meaning that the attribute must not be null. You can set it to true to allow null values.
```
static $validates_numericality_of = [
    'height' => [
        'allow_null' => true
    ]
];
```
On (Optional): The on option allows you to specify when the validation should occur. By default, it is set to 'save', which means the validation is performed when the record is saved. You can set it to 'create' to validate only during the creation of a new record or 'update' to validate only during updates.
```
static $validates_numericality_of = [
    'quantity' => [
        'on' => 'create'
    ]
];
```

Example of Usage:

class Product extends ActiveRecord\Model {
    static $validates_numericality_of = [
      'quantity' => [
        'only_integer' => true, 
        'greater_than' => 0
        ]
    ];
}

validates_numericality_of¶

`validates_numericality_of`¶