Getting a random number within a range is a very common operation. There are multiple ways of extending Swift language to add support for getting random values within a specified range. After experimenting with different implementations like utility functions, integer and float extensions I have found that the most natural way of doing it is to extend ClosedRange. This will allow to write a very readable code:
Random floating point values
1. Get a random value using a max possible range (note that arc4random_uniform excludes the upper bound).
2. Convert the value to percentage.
3. Multiply the range with the percentage.
4. Add offset to the range’s minimum value.
Random integer values
1. Get a random value from the allowed range.
2. Add the offset to the range’s minimum value.