A repository for storing code snippets to understand Swift programming, specifically iOS development with Xcode.
About Swift (https://docs.swift.org/swift-book/index.html)
Swift defines away large classes of common programming errors by adopting modern programming patterns:
- Variables are always initialized before use.
- Array indices are checked for out-of-bounds errors.
- Integers are checked for overflow.
- Optionals ensure that nil values are handled explicitly.
- Memory is managed automatically.
- Error handling allows controlled recovery from unexpected failures.
- Swift is a type-safe languages which means it is a language that encourages clear value types for code to work.
- It performs type checks when compiling code to ensure your statements and method calls do not contain conflicting types.
- Type inference is when a type is not declared but inferred during compilation based on the value which you provided.
- Comments are useful for code readability but to communicate intent or concepts to future developers.
- You can use two forward-slashes
//
for a single-line comment; anything after//
will be a comment for the remainder of the line. - You can use forward-slash asterisk
/*
and asterisk forward-slash*/
for starting and ending (respectively) a multi-line comment.
- Semi-colons are not strictly enforced to end your line of code as in other programming languages.
- It is only required if you wish to write multiple statements on a single line.
- Constants cannot be changed once set; variables can be overwritten to a different value in future.
- To declare a constant, use the keyword
let
. - To declare a variable, use the keyword
var
. - You can also declare multiple constants and variables in a single line using a comma as a delimiter:
var a = "", b = 0.0, c = true
. - You can assign almost any character including unicode characters:
let ๐ถ๐ฎ = "dogcow"
- You can print constants and variables in Swift using the system print function.
- Assume you have an initialized variable
var greeting = "Hello!"
, you can print usingprint(greeting)
.
- Though Swift does not require you to declare the type when using constants or variables, it is best to be clear for type safety.
- To declare the type, use a colon followed by a supported type:
var message: String
. - You can also declare the type for multiple constants or variables in a single line:
var a, b, c: Double
.
- Integers are whole numbers.
- The bounds for integers (x32-bit) is
-2,147,483,648
to2,147,483,647
. - For UInt (unsigned integer type), UInt is same as UInt32 (32-bit) and UInt64 on (64-bit); assign ranges using
max
andmin
properties (i.e.UInt32.min
).
- Floating-point numbers are factional numbers (containing decimals).
- Double represents 64-bit floating-point numbers; with a percision of 15 decimal digits.
- Float represents 32-bit floating-point numbers; with a percision as little as 6 decimal digits.
- Logical type which can only be true or false.
- They are great for conditional statements.
- A group of multiple values in a single compound value.
- The values of a typle can be of any type and don't need to be of the same type
let myTuple = (101, "Hello", true)
.
- An optional represent two possibilities, either there is a value and you can wrap the optional to access the underlying value, or isn't a value.
- You can set an optional to a valueless state by assigning nil.
- You cannot use nil for non-optional constants or variables.