learn-swift

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.

Type Safety and Type Inference

• 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.

Syntax & Swift Basics

Comments

• 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

• 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 and Variables

• 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 🐶🐮 = "dogcow"

Printing

• 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 using print(greeting).

Type Annotations

• 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.

Type (Integers)

• Integers are whole numbers.
• The bounds for integers (x32-bit) is -2,147,483,648 to 2,147,483,647.
• For UInt (unsigned integer type), UInt is same as UInt32 (32-bit) and UInt64 on (64-bit); assign ranges using max and min properties (i.e. UInt32.min).

Type (Floating-Point Numbers)

• 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.

Type (Booleans)

• Logical type which can only be true or false.
• They are great for conditional statements.

Data Structure (Tuples)

• 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).

Optionals

• 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.

Nil

• You can set an optional to a valueless state by assigning nil.
• You cannot use nil for non-optional constants or variables.