Tuples, for-in, Dictionary Grouping, Filtering and Set

Set’s: 

sets are used to store distinct values of same types but they don’t have definite ordering as arrays have.(sets allow only distinct values.)

var someSet = Set<Character>()     //Character can be replaced by data type of set.

Set Operations

• Intersection
• Union
• subtracting

let evens: Set = [10,12,14,16,18]

let odds: Set = [5,7,9,11,13]

let primes = [2,3,5,7]

odds.union(evens).sorted()

// [5,7,9,10,11,12,13,14,16,18]

odds.intersection(evens).sorted()

//[]

odds.subtracting(primes).sorted()

//[9, 11, 13]

Dictionary’s : 

var cities = [“Delhi”,”Bangalore”,”Hyderabad”]

var Distance = [2000,10, 620]

let cityDistanceDict = Dictionary(uniqueKeysWithValues: zip(cities, Distance))

Filtering

var closeCities = cityDistanceDict.filter { $0.value < 1000 } //Output : ["Bangalore" : 10 , "Hyderabad" : 620]

Higher order functions in Swift: Filter, Map, Reduce, flatmap, compactMap : 

higher order functions that can be used on collection types

higher order functions are functions that takes another function/closure as argument and returns it.

Dictionary Grouping

var cities = ["Delhi","Bangalore","Hyderabad","Dehradun","Bihar"]

var GroupedCities = Dictionary(grouping: cities ) { $0.first! }// Output : ["D" :["Delhi","Dehradun"], "B" : ["Bengaluru","Bihar"], "H" : ["Hyderabad"]]

JSON dynamic adding objects:

for a in res2 {

    if let nm = a["nm"] as? String, let uni = a["uni"] {

        self.dic[nm] = uni as? String

    }

}

print(self.dic)

for-in loop :

var someDict:[Int:String] = [1:"One", 2:"Two", 3:"Three"]

for (index, keyValue) in someDict.enumerated() {

   print("Dictionary key \(index) - Dictionary value \(keyValue)")

}

Tuples:

which are used to group multiple values in a single compound Value.

The values in a tuple can be of any type, and do not need to be of same type.

For example, ("Tutorials Point", 123)

Good link : https://medium.com/@abhimuralidharan/tuple-in-swift-a9ddeb314c79

EX:

Ex1)(“tuple", 1, true) //Tuple with different data types.

Ex2) var person = ("John", "Smith”)//Read values from tuple

var firstName = person.0 // John

var lastName = person.1 // Smith

Ex3)var point = (0, 0) //Assign values to tuple

point.0 = 10

point.1 = 15

point // (10, 15)

Note: Tuple are value types. When you initialize a variable tuple with another one it will actually create a copy.

var origin = (x: 0, y: 0)

var point = origin

point.x = 3

point.y = 5

print(origin) // (0, 0)

print(point) // (3, 5)