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Swift Cheat Sheet (DRAFT) by

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Defining variables

let constantVar = "Hello, World!"

var implicitVar = "Hello, World!"

var explicitVar: String = "Hello, World!"

Loop types

for x in 1...5 

Iterate through array
for item in [1, 2, 4, 5]

Iterate through dictionary
for (key, value) in ["one":1, "two":2, ...]

Switch methods
switch ["1", "2", "3", 4, 5, 6, (1, 100)] {
    case "1": 
    case "2", "3":
        print("2 or 3")
        print("No fallthrough")
    case 4...5:
        print("Interval matching")
    case (1...100, 1...100):
        print("Tuples work the same.")
        print("Required in switchs")
        print("Must be last")

TODO: _, value binding, fallthrough, where

Function signature anatomy

Argument Label
(optional) Used when calling the function
Parameter Name
Used in the implem­ent­ation of the function
Return Type
(optional) Can be a tuple for multiple return values
(optional) Causes errors to propagate up.
func FunctionName(ArgumentLabel ParameterName: String) throws -> 
<ReturnType> {

    // Code


Event handling

No language constructs available.

Error handling

 Representing errors
enum ErrorEnum: Error {
    case ErrorTypeA
    case ErrorTypeB: String

Propagating Errors Using Throwing Functions
func canThrowErrors() throws -> String

Handling Errors Using Do-Catch
do {
    try results = ThrowTypeB()
} catch ErrorEnum.ErrorTypeB(let errorString) {
    // Handle error

Converting Errors to Optional Values
let x = try? someThrowingFunction()

Disabling Error Propagation
let x = try! someThrowingFunction()