Randomizer

public protocol Randomizer : class

A class that generates random numbers.

The definition of “random” is up to the particular conforming class. For example, instead of actual random numbers, a class could return a cyclical pattern or a single repeating value. This makes it easy to swap one class out for another, such as for testing or for distinct game modes.

For every SDG class that conforms to Randomizer, two independent instances that have been initialized the same way will return the same sequence of values.

For example, in a networked game, as long as each device initializes their instance of the Randomizer the same, each device can safely rely on its local instance to return the same values as are being returned on the other devices with no risk of the game states diverging.

Warning

The above guarantee of deterministic behaviour does not apply between differing module versions.

Note

Nothing in SDG relies on the above guarantee. If you make your own conforming class and do not need or want it to be deterministic, you can safely conform to Randomizer and use its interface anyway.

Conformance Requirements:

  • func randomNumber() -> UInt64

  • Returns a random value.

    See also

    randomNumber(inRange:)

    Declaration

    Swift

    func randomNumber() -> UIntMax
  • randomNumber(inRange:) Default implementation

    Returns a random value within the specified range.

    The following information applies to the default implementation:

    • If the value returned by randomNumber() is in the allowed range, it will be returned unaltered.
    • If the value returned by randomNumber() is outside the allowed range, it will be mapped to a value in the allowed range.

    If the randomNumber() returns every possible value of UInt64 with equal probability, randomNumber(inRange:) will also return each of its possible values with equal probability. (Specifically, no modulo bias is introduced.)

    Precondition

    randomNumber() must eventually return a value in range or less than UInt64.max.rounded(.down, toMultipleOf: UInt64(range.count)).

    Default Implementation

    Returns a random value within the specified range.

    The following information applies to the default implementation:

    • If the value returned by randomNumber() is in the allowed range, it will be returned unaltered.
    • If the value returned by randomNumber() is outside the allowed range, it will be mapped to a value in the allowed range.

    If the randomNumber() returns every possible value of UInt64 with equal probability, randomNumber(inRange:) will also return each of its possible values with equal probability. (Specifically, no modulo bias is introduced.)

    Precondition

    randomNumber() must eventually return a value in range or less than UInt64.max.rounded(.down, toMultipleOf: UInt64(range.count)).

    Declaration

    Swift

    func randomNumber(inRange range: ClosedRange<UIntMax>) -> UIntMax

    Parameters

    range

    The range of acceptable values for the random number.