iOS development using Swift - Swift Basics (2)

SWIFT BASICS (2)
iOS Development using Swift
Ahmed Ali

TODAY TOPICS
• Data types
• Strings
• Mutability, comparison, and interpolation
• Collection types
• Arrays, dictionaries and their mutability
• Control flow
• Connecting UI Controls to Your Code
Ahmed Ali

DATA TYPES
• Integers
• Int
• UInt
• Floating point
• Float
• Double
• Boolean
• Bool
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DATA TYPES - TUPLES
• Multi-values in one reference
• You can pass a tuple as a method parameter, return it from a function (or method), make
it the type of a reference.
• Definition Syntax:
• var tupleVar : (Int, String)
• Assigning it a value:
• tupleVar = (5, "String value”)
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DATA TYPES - TUPLES (CONT)
• Tuples values can be access through their index number or names
• Accessing the value through its zero-based index
let intVal : Int = tupleVar.0 // equal to 5
let strVal : String = tupleVar.1 // equal to "String Value”
• Named tuple elements
let response : (errorCode: Int, errorMessage: String) =
(404, "HTTP not found")
print("Error connecting: (response.errorMessage) with error code:
(response.errorCode)")
Ahmed Ali

STRINGS
• Syntax:
• let myStr = "String value”
• Mutability (modifiable)
• If the reference is defined with var keyword then it is mutable (can be modified)
• If the reference is defined with let keyword then it is immutable (can not be modified)
• Examples:
//Valid
var myStr = "String value"
myStr += " Additional string"
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STRINGS (CONT)
• Mutability invalid example:
//Invalid
let myStr = "String value"
myStr += " Additional string"
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STRINGS (CONT)
• Comparison:
• You don’t need to call a special method to compare to string references.
• You can use the == operator is used to compare two string reference and see if they
hold the same string value.
• The === can also check against the reference it self, this operator checks if both
reference are the same, i.e refers to the same memory address.
Ahmed Ali

STRINGS (CONT)
• Interpolation
• Simple syntax:
let hello = "Hello”
let world = "World”
let symbol = "!“
let helloWorld = "(hello) (world) (symbol)"
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COLLECTION TYPES - ARRAYS
• Can hold list of values of the same type.
• Definition syntax:
let arr : Array<String> = ["val 1", "val 2", "etc..."]
//shorthand version
let arr : [String] = ["val 1", "val 2", "etc..."]
//Shorter version using type inference
let arr = ["val 1", "val 2", "etc..."]
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COLLECTION TYPES - ARRAYS (CONT)
• Access and modify array content:
//to be modified, it must be a variable
var arr = ["v1", "v2", "v3"]
println(arr[0]) //prints first element
arr[0] = "newV1" //changes first element
println(arr[0])
arr.removeAtIndex(1) //removes second element
arr.append("anotherNewValue")//appends an element
arr += ["v4", "v5"] //append more than one element
Ahmed Ali

COLLECTION TYPES - DICTIONARIES
• Can hold list of key : value pairs.
• Definition syntax:
let dict : Dictionary<String, Int> = ["A" : 15,
"B" : 16]
//shorthand version
let dict : [String: Int] = ["A" : 15, "B" : 16]
//Shorter version using type inference
let dict = ["A" : 15, "B" : 16]
Ahmed Ali

COLLECTION TYPES - DICTIONARIES (CONT)
• Access and modify dictionary content:
//to be modified, it must be a variable
var dict : Dictionary<String, Int> = ["A" : 15,
"B" : 16]
println(dict["B"]) //prints 16
dict["B"] = 30 //modifies the value of "B" key
dict["C"] = 19 //adds new key : value pairs to the dictionary
dict.removeValueForKey("A") //removes the key with its value
Ahmed Ali

CONTROL FLOW - IF
• Like any traditional if condition you are familiar with, with additional capabilities.
• Optional binding:
var dict = ["K" : 15, "G" : 16, ”A" : 5]
if let value = dict["A"]{
println(value)
}
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CONTROL FLOW - IF (CONT)
• If condition binding variable to a tuple
• We can use optional binding to map tuple values to variables
let params = ["name" : "Ahmed", "pass" : "123456"]
if let (cached, response) = performHttpRequest("login", params){
}
//or if only one value matters
if let (_, response) = performHttpRequest("login", params){
}
Ahmed Ali

CONTROL FLOW – FOR
• Traditional for loop and varieties of for each
• Traditional for loop:
let arr = [1, 2, 3, 4, 5, 6, 7]
//The parentheses here are mandatory in this old style for loop
for (var i = 0; i < arr.count; i++){
}
Ahmed Ali

CONTROL FLOW – FOR EACH
• For each
• Removing the parentheses is mandatory for all varieties of for each loop
• For each with open range operator:
for i in 0 ... 10 {
//this loop will loop from the value 0 to the value 10 (11 loops)
}
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CONTROL FLOW – FOR EACH (CONT)
• For each with half open operator:
for i in 0 ..< 10 {
//this loop will loop from the value 0 to the value 9 (10 loops)
}
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CONTROL FLOW – FOR EACH (CONT)
• For each with arrays:
let arr = [1, 2, 3, 4, 5, 6, 7]
for element in arr{
}
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CONTROL FLOW – WHILE AND DO .. WHILE
• While and do .. While, has nothing different than what you already from Java, C, C++ or
PHP.
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• No implicit fallthrough.
• No need for break statements.
• Use fallthrough if you want the
case to fallthrough.
• Switch cases can be against non-numeric
types.
• Switch cases are exhaustive: all
possible values must have a matching
case.
• Have many varieties to handle range
matches, tuple mapping, where
conditions, and bindings.
let myConst = 2;
switch myConst{
case 1:
println("myConst = 1")
case 2:
case 3:
default:
println("myConst = (myConst)")
}
CONTROL FLOW - SWITCH
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CONTROL FLOW – SWITCH (CONT)
• Range matching example
• Note: all possible numeric values must
have a matching case, so a default
case is mandatory.
switch myConst{
case 0 ... 4:
println("myConst is between 0 and
4")
case 5 ... 50:
50")
case 51 ..< 60:
59")
default:
}
Ahmed Ali

• Fallthrough example
• If the second case is matched, it’ll
cause all the cases beneath it to be
executed as well.
• switch myConst{
• case 0 ... 4:
• println("myConst is between 0 and 4")
• case 5 ... 50:
• //if this case matched, it'll pass execution to
the all the cases beneath it
• fallthrough
• case 51 ..< 60:
• default:
• println("myConst = (myConst)")
• }
Ahmed Ali

• let x where ?
• Binding and where conditions
switch myConst{
case let x where x >= 0 && x < 5:
println(x);
case 6..<9:
println("between 6 and 8")
case 9, 10, 11, 12:
default:
}
Ahmed Ali

Connecting UI Controls to Your
Code

iOS development using Swift - Swift Basics (2)

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