# AbstractGenerator Class - [Overview](#overview) - [Properties](#properties) - [Methods](#methods) ## Overview The `AbstractGenerator` class is the base class implemented by all generator classes of the Keygen package, including the `Keygen` class. It implements the `GeneratorInterface` interface - which requires that a `generate()` method must be implemented by all abstract generators. The `AbstractGenerator` class provides the basic functionalities for all key generators. > **

Abstract Class

** > The `AbstractGenerator` class is defined as an abstract class - hence, its constructor cannot be called with the `new` keyword. It is meant to be extended by specialised sub-classes.
The `AbstractGenerator` class has two direct sub-classes namely: - **

`Generator` class

** This is the parent class of all the built-in generators. It provides specialised functionality for _key exclusions_ and handling the key generation logic, which includes: applying key transformations and adding affixes to generated keys. See [Generator Class] for more details about the `Generator` class.
- **

`Keygen` class

** The `Keygen` class acts as a [facade] to provide access to all the functionalities of the built-in key generators via lots of convenience methods. It is overloaded to provide dynamic methods for creating instances of specialized generators. See [Keygen Class] for more details about the `Keygen` class.
## Properties - **

`length`

** This is an `integer` that specifies the length of keys to be generated by the generator. It defaults to `16` if no length has been specified. See [Key Length] to learn more about defining key length.
- **

`prefix`

** This is the `string` that will be prepended to keys generated by the generator (_affixed to the beginning of generated keys_). It returns `null` if no prefix has been specified. See [Key Affixes] to learn more about using prefixes.
- **

`suffix`

** This is the `string` that will be appended to keys generated by the generator (_affixed to the ending of generated keys_). It returns `null` if no suffix has been specified. See [Key Affixes] to learn more about using suffixes.
- **

`inclusiveAffix`

** This is a `boolean` flag that determines whether the key length should include the length of the affixes (prefix and suffix) - this is known as _affix inclusion_. `true` indicates that the key length should include the affix length. The default value is `true`. See [Key Affixes] to learn more about affix inclusion.
- **

`randomLength`

** This is a `boolean` flag that indicates whether the generator should generate keys of random length. If this flag is `true`, the `length` property of the generator is ignored and keys of random length are generated. The default value is `false`. See [Key Length] to learn more about creating random length keys.
- **

`transformations`

** This is an `array` that represents a queue of key transformations that have been registered on the generator. See [Key Transformations] to learn more about using key transformations.
- **

`mutable`

** This is an `array` that represents a collection of mutable generator properties that have been specified for the generator. See [Key Mutations] to learn more about mutable generator properties.
- **

`immutable`

** This is an `array` that represents a collection of immutable generator properties that have been specified for the generator. See [Key Mutations] to learn more about immutable generator properties.
## Methods > **

Return Values

** > All methods of the `AbstractGenerator` class, except the `generate()` method, return the generator instance on which they are called. This offers the flexibility of using [method chaining] to execute methods on the generator. - **

`length(int|bool $length [, bool $propagateMutation = true])`

** The `length()` method defines the key length of the generator. If the `$length` argument is `false`, then the `randomLength` property is set to `true` - and keys of random length will be generated. Otherwise, if it is not a valid numeric length value, an `InvalidLengthKeygenException` is thrown. See [Key Length] to learn more about defining key length.
> **

`$propagateMutation`

** > The `$propagateMutation` argument is a boolean that indicates if the change in the length property should be adopted by linked generators in the mutates collection of the generator. It defaults to `true` if not specified. This is the second argument of all setter methods for mutable properties: `length()`, `prefix()` and `suffix()` methods. See [Key Mutations] to learn more about mutation propagation. - **

`prefix(string|bool $prefix [, bool $propagateMutation = true])`

** The `prefix()` method sets the prefix string of the generator. If the `$prefix` argument is `false`, it clears any existing prefix on the generator. Otherwise, if it is not a valid affix value, an `InvalidAffixKeygenException` is thrown.
- **

`suffix(string|bool $suffix [, bool $propagateMutation = true])`

** The `suffix()` method sets the suffix string of the generator. If the `$suffix` argument is `false`, it clears any existing suffix on the generator. Otherwise, if it is not a valid affix value, an `InvalidAffixKeygenException` is thrown.
- **

`affix(string|bool $prefix = null [, string|bool $suffix = null])`

** The `affix()` method is a convenience method that sets the prefix and suffix strings of the generator with a single call. The `$prefix` argument sets the prefix string of the generator, while the `$suffix` argument sets the suffix string. If any of the values is not a valid affix value, an `InvalidAffixKeygenException` is thrown.
- **

`inclusiveAffix(bool $flag)`

** The `inclusiveAffix()` method enables or disables _affix inclusion_ on the generator. If the `$flag` argument is set to `true`, affix inclusion is enabled; otherwise, it is disabled.
- **

`transformation(array|callable $transformation [...])`

** The `transformation()` method appends the specified transformation or collection of transformations to the transformations queue. The `$transformation` argument must be a `callable` or an `array` that contains only callables, otherwise an `InvalidTransformationKeygenException` is thrown.
- **

`transformations(array|callable $transformation [...])`

** The `transformations()` method resets the transformations queue and starts a new queue with the specified transformation or collection of transformations. The `$transformation` argument must be a `callable` or an `array` that contains only callables, otherwise an `InvalidTransformationKeygenException` is thrown. If `$transformation` is set to an empty array (`[]`), the transformations queue is emptied. [facade]: [Generator Class]: <./generator.md> [Keygen Class]: <./keygen.md> [Key Length]: <./key-length.md> [Key Affixes]: <./key-affixes.md> [Key Mutations]: <./key-mutation.md> [Key Transformations]: <./key-transformation.md> [method chaining]: