String Functions and Operators in Swift
A string is a sequence of characters that is either composed of a literal constant or the same kind of variable. For eg., “Hello World” is a string of characters. In Swift4, a string is Unicode correct and locale insensitive. We are allowed to perform various operations on the string like comparison, concatenation, iteration, and many more.
We can create a string either by using a string instance or creating an instance of a string class. The following are the commonly used methods to create a string in Swift:
By using String Instance
To create a string we can use a String() initializer. It will create an instance of a string.
Syntax:
var str = String(“Hello GFG)
Example:
Swift
// Swift program to illustrate how to create a string // Here String() is used for string instance var s = String ( "Hello Everyone!!!" ) print (s) |
Output:
Hello Everyone!!!
By using String Literal
Here, we use double apostrophes on the words for the formation of strings, similar as, normal strings in other languages. Or we can use a String data type to create a string type variable.
Syntax:
var str = ” Welcome”
var s:String = “Hello”
Example:
Swift
// Swift program to illustrate how to create a string // Create strings var str1 = "Hello Everyone" print (str1) var str2: String = "Welcome Everyone" print (str2) |
Output:
Hello Everyone Welcome Everyone
Multi-line Strings
Apart from single-line strings, we can also create multi-line strings. For the creation of multi-line strings, instead of double quotes, we have to use triple quotes at the end and start of the string(“””).
Syntax:
var str = “””
Hello world
How are you ?
“””
Example:
Swift
// Swift program to illustrate how to create multi-line string // Creating multi-line string let str = "" " Hello People!!! This is an example of multiline string "" " print (str) |
Output:
Hello People!!! This is an example of multiline string
String Functions and Operators
Now, we will see some commonly used functions and operators related to a string:
Empty String
Empty string is a type of string whose length is equal to zero. Or in other words, it’s a sequence of zero characters in a string. For creating an empty string, either we can create a string literal with single quotes only or by passing an argument with no values in it. Sometimes people get confused between an empty string and a null string. Null string means which has no value at all in it. In other words, it can also be defined as the absence of a string instance.
Example:
Swift
// Swift program to create empty string // With empty string literal var Q = "" // With no values passed in an argument var E = String () |
isEmpty
Swift provides an inbuilt property to check whether the given string is empty or not. It will return true if the given string is empty. Otherwise, it will return false.
Syntax:
str.isEmpty
Example:
Swift
// Swift program to illustrate isEmpty property // Creating a string var str1 = "" // Checking if the given string is empty or not if str1.isEmpty { print ( "str1 is empty" ) } else { print ( "str1 is not empty" ) } // Creating another string let str2 = "hello Jeevan" // Checking if the given string is empty or not if str2.isEmpty { print ( "str2 is empty" ) } else { print ( "str2 is not empty" ) } |
Output:
str1 is empty str2 is not empty
String Length
The length of a string can be defined as the total number of characters present in the string. The Count property is used for counting the length of the string. The length of an Empty string is zero.
Syntax:
str.count
Example:
Swift
// Swift program to illustrate count property // Creating a string var s = "Hello Sudha! How are you?" // Count property is used to count the length of the string. var len = s. count print ( "Length of str is \(len)" ) |
Output:
Length of str is 25
String Concatenation
Concatenation is the addition of one or more strings to the end of another string. For string literals and string constants, concatenation occurs at compile time. For string variables, concatenation occurs only at run time. For the concatenation of strings, we have to use the ‘+’ operator to concatenate either strings or strings, or strings and characters, or characters and characters.
Syntax:
var s = string1 + string2
Example:
Swift
// Swift program to illustrate string concatenation // Creating strings var str1 = "Hello" var str2 = " People!" var str3 = "My" var str4 = "Name" var str5 = "is" var str6 = "Max." // Concatenating two strings using + operator var s1 = str1 + str2 print (s1) // Concatenating multiple strings using + operator var s2 = str3 + " " + str4 + " " + str5 + " " + str6 print (s2) |
Output:
Hello People! My Name is Max.
String Comparison
To check whether the given strings are the same or not we use equal to(==), and not Equal to(!=) operators. Both operators are the most commonly used operator to compare two strings. Here both the operators return true if the given strings fulfill the condition. Otherwise, return false.
Syntax:
string1 == string2
or
string1 != string 2
Example:
Swift
// Swift program to illustrate string comparison // Creating strings var str1 = "hello" var str2 = "hello" var str3 = "Krishna" // Comparing the equality of two strings if (str1 == str2) { print ( "\(str1) is equal to \(str2)" ) } else { print ( "\(str1) is not equal to \(str2)" ) } // Comparing the not equality of two strings if (str1 != str3) { print ( "\(str1) is not equal to \(str3)" ) } else { print ( "\(str1) is equal to \(str3)" ) } |
Output:
hello is equal to hello hello is not equal to Krishna
Greater than Operator
To check if the given string is greater than another string we use the greater than operator(>). Here, > operator returns true if the first string is greater than another string. Otherwise, it will return false.
Syntax:
string1>string2
Example:
Swift
// Swift program to check if the given string // is greater than another string or not // Creating strings var str1 = "hen" var str2 = "cow" // Finding largest string if (str1 > str2) { print ( "\(str1) is greater than \(str2)" ) } else { print ( "\(str1) is not greater than \(str2)" ) } |
Output:
hen is greater than cow
Less than Operator
To check if the given string is less than another string we use the less than operator(<). Here, < operator returns true if the first string is less than another string. Otherwise, it will return false.
Syntax:
string1<string2
Example:
Swift
// Swift program to check if the given string // is less than another string or not // Creating strings var str1 = "Ant" var str2 = "cow" // Finding largest string if (str1 < str2) { print ( "\(str1) is less than \(str2)" ) } else { print ( "\(str1) is not less than \(str2)" ) } |
Output:
Ant is less than cow
hasPrefix(prefix: String)
This function is used to check whether a given parameter string exists as a prefix of the string or not. If the string exists as a prefix in the other string, then it will return true. Otherwise, return false.
Syntax:
string1.hasPrefix(string2)
Example:
Swift
// Swift program to illustrate hasPrefix() function // Creating strings var string1 = "hello Suman" var string2 = "hell" // Checking whether a given parameter string exists // as a prefix of the string or not var result = string1.hasPrefix(string2) print ( "Does string1 starts with string2? \(result)" ) |
Syntax:
Does string1 starts with string2? true
hasSuffix(suffix: String)
This function is used to check whether a given parameter string exists as a suffix or not. If the string exists as a suffix in the other string, then it will return true. Otherwise, return false.
Syntax:
string1.hasSuffix(str2)
Example:
Swift
// Swift program to illustrate hasSuffix() function // Creating strings var string1 = "hello Suman" var string2 = "man" // Checking whether a given parameter string exists // as a suffix of the string or not var result = string1.hasSuffix(string2) print ( "Does string1 ends with string2 : \(result)" ) |
Output:
Does string1 ends with string2 : true
String.lowercased()
Lowercase means small letter alphabets. Here, we use this function for the conversion of all characters into lowercase characters in the given string.
Syntax:
string.lowercased()
Example:
Swift
// Swift program to illustrate lowercased() function // Creating strings var string = "Hello People" // Conversion of every characters of the string into lowercase var result = string.lowercased() print ( "Original String: \(string)" ) print ( "Lowercase String: \(result)" ) |
Output:
Original String: HellO PeoPle Lowercase String: hello people
String.uppercased()
Uppercase means capital letter alphabets. Here, we use this function for the conversion of all characters into uppercase characters in the given string.
Syntax:
String.uppercased()
Example:
Swift
// Swift program to illustrate uppercased() function // Creating strings var string = "HellO PeOpLe" // Conversion of every characters of the // string into uppercase var result = string.uppercased() print ( "Original String : \(string)" ) print ( "Uppercase String : \(result)" ) |
Output:
Original String : HellO PeOpLe Uppercase String : HELLO PEOPLE
String.reversed()
Reversing a string means changing the order of a given string so that the last character of the string becomes the first character of the string and so on. This function is used for doing the reverse of the given string. With the help of this function, we can also check whether the string is ‘Palindrome’ or not. Palindrome means the sequence of characters which reads the same from backward as well as forwards, like, noon.
Syntax:
String. reversed()
Example:
Swift
// Swift program to illustrate reversed() function // Creating string var string = "Hello People" // Reversing the string var result = String (string.reversed()) // Print the output print ( "Original String : \(string)" ) print ( "Reversed String : \(result)" ) |
Output:
Original String : Hello People Reversed String : elpoeP olleH
String.insert()
This function is used for inserting a character at a specified index in the string.
Syntax:
string1.insert(ch, at: I)
where ‘ch’ defines the character which has to be inserted and ‘i’ defines the index of the string at which ‘ch’ is to be inserted
Example:
Swift
// Swift program to illustrate insert() function // Creating string var string1 = "Hello People!" var ch : Character = "x" var i = string1.index(string1.startIndex, offsetBy: 5) // Here, character 'x' is inserted at the position 'i' // which is here 5 in the string. string1.insert(ch, at: i) // Printing the output print (string1) |
Output:
Hellox People!
String.remove(at:)
This function is used for removing characters at a specified index in the string.
Syntax:
string1.remove(at: I)
where ‘i’ is the index in the string from which the character will get removed.
Example:
Swift
// Swift program to illustrate remove() function // Creating string var str1 = "Hello People!" print ( "Original string: \(str1)" ) // String's index which has to be removed var i = str1.index(str1.startIndex, offsetBy: 6) // Function 'remove' is used var removed = str1.remove(at: i) print ( "String after remove() : \(str1)" ) print ( "Character Removed : \(removed)" ) |
Output:
Original string: Hello People! String after remove() : Hello eople! Character Removed : P
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