A dictionary in Swift is an unordered collection of key-value pairs where keys must be unique. It allows storing multiple values of the same type associated with unique keys of the same type. Dictionaries are initialized using a dictionary literal containing key-value pairs separated by commas within square brackets. Values can be accessed, updated, added or removed using their unique keys.

1. DICTIONARIES
• A dictionary is an unordered collection that
stores multiple values of the same type.
• Each value from the dictionary is associated
with a unique key.
• All the keys of one dictionary must have the
same type.
• All the values of one dictionary must have the
same type.

2. DICTIONARIES
• The type of a dictionary is determined by the
type of the keys and the type of the values.
• For example a dictionary of type[String:Int] has
keys of type String and values of type Int.
• Unlike arrays, items in dictionary do not have a
specified ordered.
• Each key of one dictionary must be unique.

3. DICTIONARIES
• Syntax:
var Identifer: [KeyType:ValueType]
• Example:
var myDictionary: [String:Int]

4. DICTIONARIES
• You can initialize a dictionary with a dictionary
literal.
• A dictionary literal is a list of key-value pairs,
separated by commas, surrounded by a pair of
square brackets.
• A key-value pair is a combination of a key and
a value separate by a colon(:).

5. DICTIONARY LITERAL
• Syntax:
var Identifer: [KeyType:ValueType] = [key:value,
key:value, ...]
• Example:
var dictionary: [String:Int] =[ "one" : 1,
"two" : 2,
"three" : 3 ]

6. EMPTY DICTIONARIES
• Similar to arrays there can be empty
dictionaries in Swift.
• You can create empty dictionary using the
empty dictionary literal ([:]).
• Example:
var myEmptyDictionary: [String:Int] = [:]

7. CREATING & ITERATING DICTIONARY
var info: [String: String] = [
"first_name" : "Raj",
"last_name" : "Sharma",
"job_title" : "Singer"
]
for (key, value) in info
{
print("(key): (value)")
}
OUTPUT
job_title: Singer
last_name: Sharma
first_name: Raj

8. CREATING & ITERATING DICTIONARY
var info: [String: String] = [
"first_name" : "Raj",
"last_name" : "Sharma",
"job_title" : "Singer"
]
for item in info
{
print(item)
}
OUTPUT
("job_title", "Singer")
("last_name", "Sharma")
("first_name", "Raj")

9. ACCESSING DICTIONARY
var info: [String: String] = [
"first_name" : "Raj",
"last_name" : "Sharma",
"job_title" : "Singer"
]
print(info["first_name"]) OUTPUT
Raj

10. Use of nil in Dictionary
var info: [String: String] = [
"first_name" : "Raj",
"last_name" : "Sharma",
"job_title" : "Singer"
]
info["first_name“] = nil
for item in info
{
print(item)
}
OUTPUT
("job_title", "Singer")
("last_name", "Sharma")

11. PROPERTIES OF DICTIONARY
• count
• isEmpty
• keys
• values

12. ACCESSING DICTIONARY KEYS
var info: [String: String] = [
"first_name" : "Raj",
"last_name" : "Sharma",
"job_title" : "Singer"
]
for i in info.keys
{
print(i)
}
OUTPUT
first_name
last_name
job_title
OUTPUT
last_name
job_title
first_name
OUTPUT
job_title
last_name
first_name

13. ACCESSING DICTIONARY VALUES
var info: [String: String] = [
"first_name" : "Raj",
"last_name" : "Sharma",
"job_title" : "Singer"
]
for i in info.values
{
print(i)
}
OUTPUT
Raj
Sharma
Singer
OUTPUT
Singer
Sharma
Raj
OUTPUT
Sharma
Raj
Singer

14. UPDATE PAIR/ITEM INTO DICTIONARY
var info: [String: String] = [
"first_name" : "Raj",
"last_name" : "Sharma",
"job_title" : "Singer"
]
info[“last_name"] = "Kaur"
info.updateValue("Jaya",forKey:"first_name")

15. ADDING PAIR/ITEM INTO DICTIONARY
var info: [String: String] = [
"first_name" : "Raj",
"last_name" : "Sharma",
"job_title" : "Singer"
]
info["middle_name"] = "Vig"
print(info.count)
OUTPUT
4

16. REMOVE PAIR/ITEM FROM DICTIONARY
var info: [String: String] = [
"first_name" : "Raj",
"last_name" : "Sharma",
"job_title" : "Singer"
]
info.removeValue(forKey: "job_title")
print(info.count)
OUTPUT
2

17. METHODS OF DICTIONARIES
• removeValue(forkey:key)
• removeAll
• updateValue(value,forkey:key)

18. COMPARING DICTIONARIES
var d1 = ["name": "Tim", "surname": "Cook"]
var d2 = ["name": "Kate", "surname": "Perry"]
// Check if they are the same
if d1==d2 {
print("D1 is same as D2")
}
else {
print("D1 is not same as D2")
}
OUTPUT
D1 is not same as D2

19. COMPARING DICTIONARIES
var d1 = ["name": "Tim", "surname": "Cook"]
var d2 = ["name": “Tim", "surname": “Cook"]
// Check if they are the same
if d1==d2 {
print("D1 is same as D2")
}
else {
print("D1 is not same as D2")
}
OUTPUT
D1 is same as D2

20. COMPARING DICTIONARIES
var d1 = ["name": "Tim", "surname": "Cook"]
var d2 = ["name": “TiM", "surname": “Cook"]
// Check if they are the same
if d1==d2 {
print("D1 is same as D2")
}
else {
print("D1 is not same as D2")
}
OUTPUT
D1 is not same as D2