Awesome
Coursera Swift coding guidelines
General
- No semicolons, unless they are required.
- No parentheses, unless they are required.
- Each variable or constant must be on a separate line.
let
is preferred,var
is only used when mutability is strictly required.- Always use named parameters.
- Indentation = 4 spaces (no TABs).
Variables or constants
- Avoid using self to keep code clean. Swift does not require the use of self. Use self only when absolutely needed.
- Use type inference as far as possible.
Preferred
let course = "Course"
var courseTitle: String
Not preferred
let course: String = "Course"
Ordering instance variables
Order the instance variables in the class, with this order:
- Immutable
- Optional immutable
- Variables
- Optional variables
If-Else
if let name = optionalName {
greeting = "Hello, \(name)"
} else {
greeting = "Bye"
}
Optionals
Use if let
syntax if the unwrapping involves more than 1 statement or when the optional is to be used as a conditional.
Use ?
in other cases.
Example:
if let unwrapped = optional {
unwrapped statement 1;
unwrapped statement 2;
}
optional?.optionalFunction() // evaluates to nil if optional is not present
Use optional chaining when you need to go through a series of optionals.
Example:
if let validCorgis = coursera.mobileTeam?.coreTeam?.corgis {
validCorgis
}
Classes
- Class prefixes are not needed.
Functions
- Always use named parameters when using tuples in functions using the
#
parameter. - Nest functions whenever possible.
Example:
func findIndexOfString(#inputString: String, #array: [String]) -> (index: Int?, name: String?) {
for (index, value) in enumerate(array) {
if (value == string) {
return (index, string)
}
}
return (nil, nil)
}
KVO
- Functional Guidelines
- If a class wants to KVO a property then it must supply a class context.
- Super should be called in the KVO observation function.
- Always remove observer on deinit.
- Style Guidelines
- Each KVO key path match should call its own update/changed function.
- Switch statements are often the best way to follow the logical 'return-first' guideline for the observer function.
- Remember, in Swift cases do not fall-through by default.
Example:
import Foundation
class ClassB: NSObject {
var someProperty: Int = 0
}
private var NewClassKVOContext = "NewClassKVOContext"
class NewClass: NSObject {
var classB: ClassB
override init() {
classB = ClassB()
super.init()
classB.addObserver(self, forKeyPath: "someProperty", options: .Initial | .New, context: &newClassKVOContext)
}
// MARK: KVO Methods
override func observeValueForKeyPath(keyPath: String!, ofObject object: AnyObject!, change: [NSObject : AnyObject]!, context: UnsafeMutablePointer<Void>) {
if context != &newClassKVOContext {
super.observeValueForKeyPath(keyPath, ofObject: object, change: change, context: context)
return
}
switch keyPath {
case "someProperty":
somePropertyChanged(change[NSKeyValueChangeNewKey])
default:
super.observeValueForKeyPath(keyPath, ofObject: object, change: change, context: context)
}
}
func somePropertyChanged(someProperty: AnyObject?) {
if let validSomeProperty = someProperty as? Bool {
// Do something
}
}
// MARK: Deinit
deinit {
classB.removeObserver(self, forKeyPath: "someProperty", context: &newClassKVOContext)
}
}