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84 lines
2.9 KiB
Markdown
84 lines
2.9 KiB
Markdown
# iOSProgrammingGuidelines
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## Swift
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### Type vs instance methods
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If a method is independent of instance state it should be declared as type method, preferably by using `static` keyword (or `class` in case when the method is designed to be overridden in a subclass).
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> This is to avoid methods giving a false impression that they are dependent on the instance state while in fact they are not.
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### Controlling subclassing behavior
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Subclassing behavior should be designed with maximal hermetization principle in mind - choosing most restrictive access level possible.
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Declare class `final` unless you explicitly design it to be inheritable. For non final class declare all instance members as `final` and type members as `static` except for those you explicitly design for overriding.
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When designing a module prefer `public` for non final class unless you explicitly design it to be inheritable by external clients. For `open` class prefer `public` for members except for those you explicitly design for overriding by external clients.
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> Every point that can be overridden increases complexity, thus it should always be a conscious choice to add it.
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### Avoid force unwrapping
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Use `guard` and `fatalError()` instead of force unwrapping to clarify your intent.
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```swift
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guard let value = optionalValue else { fatalError("reason why value must be present") }
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```
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> This is to avoid situations in which reason for force unwrapping is undocumented.
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### Place noop comment in functions left empty by intention
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```swift
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func didDeliver(parcel: Parcel) {
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// noop
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}
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```
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> This is to make clear function is empty by intention and not by mistake
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### Declarations
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Do not declare type if compiler is able to infer it.
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```swift
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let string = "a string"
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let double = 1.0
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let int = 1
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let array = [1, 2, 3]
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let dictionary = [1: "one", 2: "two"]
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```
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> This is to minimize clutter.
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Keep type on the right hand side of assignment operator (this rule does not apply for closures, declare the type wherever it helps readability).
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```swift
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let height = CGFloat(44)
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let duration = NSTimeInterval(0.25)
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let view = UIView()
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var array = [Int]()
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var dictionary = [Int: String]()
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let accumulator: (Int, Int) -> Int = { $0 + $1 }
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```
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> Since not all the types can be declared by a literal and type on the left hand side of assignment operator (e.g. `let height: CGFloat = 20`), let's keep all the types on the right side.
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Declare constants within appropriate type.
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```swift
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class PhysicalObject {
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/// N * m^2 * kg^-2
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static let gravitationalConstant = 6.667e-11
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}
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```
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> This is to increase discoverability and avoid global namespace pollution.
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Gather IBOutlets in one group above all the other properties and keep them private.
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```swift
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@IBOutlet private weak var view: UIView!
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```
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> Outlets are implementation detail and should be kept private. Gathering them in one grup above all the other properties is old convention.
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