Integers

Swift provides signed and unsigned integers in 8, 16, 32, and 64 bit forms. These integers follow a naming convention similar to C, in that an 8-bit unsigned integer is of type UInt8, and a 32-bit signed integer is of type Int32. Like all types in Swift, these integer types have capitalized names.

Integer Bounds

It is okay to get the minimum & maximum values of each integer type with its min & max properties.

let minValue = UInt8.min // 0 with UInt8 type
let maxValue = UInt8.max // 255 with UInt8 type

Int

In most cases, we don’t need to pick the specific size of integer. Just use Int would be enough.

• On a 32-bit platform, Int is the same size as Int32.

• On a 64-bit platform, Int is the same size as Int64.

Unless we need to specify the size of integer, normally, use Int would be enough and could help increasing code consistency and interoperability. ex: 32bit platform Int could also store any value between -2,147,483,648 ~ 2,147,483,647, and is large enough for many integer ranges.

UInt

Swift also provide unsigned integer type UInt, same as Int:

• On a 32-bit platform, Int is the same size as Int32.

• On a 64-bit platform, Int is the same size as Int64.

Note

Use UInt only when you specifically need an unsigned integer type with the same size as the platform’s native word size. If this isn’t the case, Int is preferred, even when the values to be stored are known to be nonnegative. A consistent use of Int for integer values aids code interoperability, avoids the need to convert between different number types, and matches integer type inference, as described in Type Safety and Type Inference.

Floating-Point Numbers

The numbers with a fractional component. Floating-point types can represent much wider range of values than integer types. and can store numbers much larger or smaller than Int. Swift provide 2 signed floating-point number types:

• Double represents a 64-bit floating-point number.

• Float represents a 32-bit floating-point number.

Note

Double has a precision of at least 15 decimal digits, whereas the precision of Float can be as little as 6 decimal digits. The appropriate floating-point type to use depends on the nature and range of values you need to work with in your code. In situations where either type would be appropriate, Double is preferred.

References

https://docs.swift.org/swift-book/LanguageGuide/TheBasics.html