Variables and Constants
The purpose of this is just to document my journey into iOS and Swift 4 programming. A place I can reference to help me solidify what I have learned and help others along the way. I have been programming in swift for a few months now. Documenting the stuff I learn is something I wish did throughout my career as a developer when studying other languages and technology, so I thought I would start now.
The let and var keywords
The var keyword creates a variable
mutable can be changed
The let keyword creates a constant
immutable is set and can not be changed
I have read you should avoid using var and use let first changing the let to var later which I guess is just good programming practice if the data isn’t going to change it should be a constant.
This is not Python
You won’t see any snake_case in swift
You write Swift variables and constants using camelCase
firstName: String lastName: String emailAddress: String
At first I hated this but I soon got used to it and I now find it more readable. If you have initial type which can be inferred you omit the type annotation as you can see what it is.
let firstName: String firstName = "Matthew" // This could just be the following as the string type can be inferred. let firstName = "Matthew" //The let keyword makes firstName a constant so it can no longer be changed trying to do so will result in an error. firstName = "Chris" // cannot assign to value: 'firstName' is a 'let' constant var lastName: String lastName = "Shirtliffe" let wearsGlasses = true var age: Int age = 30 var age = 30 let companyName = "Space Labs Digital" // Do this var nameOfVar: String // Dont do this var nameOfVar : String
Single line lets and vars
var a=1, b=2, c=3 let x=4, y=5, z=6
Have to print variables and constants?
var a=1, b=2, c=3 print(a) print(b) print(b) print("value of a is \(a)") print("value of b is \(b)") print("value of c is \(c)")
Common Data Types
You can install Swift 4 on your mac and ubuntu but I’ll let you use google to find out how to do that.
Running swift code using the Terminal
mkdir project_name cd swift_playground
Create project structure
swift package init --type executable
Run swift app
Running swift code using XCode in a playground
Some let and var tips
- camelCase your var and let names the first character lowercase not snake_case
- add 1 space after colon for type annotation var name: <-space here before datatype
- Pass by copy
- var can be changed (Mutable)
- let can not be changed (immutable) try changing after will cause an error
- set at let first then change to var later
- not exclusive to swift but avoid abbreviations x, y
- constants using the let keyword can be declare first and assigned later.
Swift Style Guides
git clone https://github.com/raywenderlich/swift-style-guide.git
git clone https://github.com/linkedin/swift-style-guide