This tutorial belongs to the Swift series
In Swift, numbers have 2 main types: Int
and Double
.
An Int
is a number without decimal point.
A Double
is a number with decimal point.
Both use 64 bits, on modern computers that work with 64 bits, and 32 bit on 32bit platforms.
The range of values they can store depends on the platform used, and can be retrieved using the int
property of each type:
Then, in addition to Int
and Double
, we have lots of other numeric types, mostly used to interact with APIs built in the past and that needed to interact with C or ObjectiveC, and you must be aware that we have them:

Int8
is an integer with 8 bits 
Int16
is an integer with 16 bits 
Int32
is an integer with 32 bits 
Int64
is an integer with 64 bits 
UInt8
is an unsigned integer with 8 bits 
UInt16
is an unsigned integer with 16 bits 
UInt32
is an unsigned integer with 32 bits 
UInt64
is an unsigned integer with 64 bits
UInt
is like Int
, but unsigned, and it ranges from 0 to Int.max * 2
.
Float
is a decimal number with 32 bits.
Then using Cocoa APIs you might use other numeric types like CLong, CGFloat, and more.
You will always use Int
or Double
in your code, and use those specific types to particular cases.
Any of those types can always be converted to Int
and Double
types, instantiating a number passing the value inside parentheses to Double()
or Int()
:
let age : UInt8 = 3
let intAge = Int(age)
You can also convert a number from Double
to Int
:
let age = Double(3)
let count = Int(3.14)