Functions

functions

Mutable variables as parameters

Hacking With Swift

nshipster | method-swizzling

Result return value Discard

Discardable result

You are getting this issue because the function you are calling returns a value but you are ignoring the result.

There are two ways to solve this issue:

1. Ignore the result by adding _ = in front of the function call

2. Add @discardableResult to the declaration of the function to silence the compiler

@discardableResult
func doSomething() -> String { return "Custom String"}

doSomething()

let _ = doSomething()

Selector Obj C

Unrecognized Selector Sent To Instance

unrecognized-selector

Variadic Parameters

You can skip using array type in the API definition and use variadic parameters introduced in Swift 5.0

extension Canvas {
    func add(_ shapes: Shape...) {
        shapes.forEach(add)
    }
}

let circle = Circle(center: CGPoint(x: 5, y: 5), radius: 5)
let lineA = Line(start: .zero, end: CGPoint(x: 10, y: 10))
let lineB = Line(start: CGPoint(x: 0, y: 10), end: CGPoint(x: 10, y: 0))

let canvas = Canvas()
canvas.add(circle, lineA, lineB)
canvas.render()

Code snippet by Swift by Sundell