How to find the Index of Substring in Swift - Step by Step Examples

How to find the Index of Substring in Swift ?

Answer

To find the index of a substring in Swift, you can use the range(of:) method of the String class. This method returns the range of the first occurrence of the specified substring, which you can then use to determine the starting index.

✐ Examples

1 Finding the index of "World" in "Hello World"

In this example,

We create a string named str with a value of "Hello World".
Next, we define a substring substring with a value of "World" that we want to find in the main string.
We use the range(of:) method of the string str to find the range of the first occurrence of the substring. This method returns an optional range, so we use optional binding (if let) to safely unwrap the result.
If the substring is found, the range constant will hold the range of the substring within the main string. We then calculate the starting index of this range by converting the range's lower bound to an integer offset from the string's start index using the distance(from:to:) method.
Finally, we print the starting index of the substring within the main string.
If the substring is not found, we print a message indicating that the substring was not found.

Swift Program

import Foundation

let str = "Hello World"
let substring = "World"
if let range = str.range(of: substring) {
    let index = str.distance(from: str.startIndex, to: range.lowerBound)
    print("The starting index of \"(substring)\" is: (index)")
} else {
    print("Substring \"(substring)\" not found")
}

Output

The starting index of "World" is: 6

2 Finding the index of "Prog" in "Swift Programming"

In this example,

We create a string named str with a value of "Swift Programming".
Next, we define a substring substring with a value of "Prog" that we want to find in the main string.
We use the range(of:) method of the string str to find the range of the first occurrence of the substring. This method returns an optional range, so we use optional binding (if let) to safely unwrap the result.
If the substring is found, the range constant will hold the range of the substring within the main string. We then calculate the starting index of this range by converting the range's lower bound to an integer offset from the string's start index using the distance(from:to:) method.
Finally, we print the starting index of the substring within the main string.
If the substring is not found, we print a message indicating that the substring was not found.

Swift Program

import Foundation

let str = "Swift Programming"
let substring = "Prog"
if let range = str.range(of: substring) {
    let index = str.distance(from: str.startIndex, to: range.lowerBound)
    print("The starting index of \"(substring)\" is: (index)")
} else {
    print("Substring \"(substring)\" not found")
}

Output

The starting index of "Prog" is: 6

Summary

In this tutorial, we learned How to find the Index of Substring in Swift language with well detailed examples.

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How to find the Index of Substring in Swift - Step by Step Examples

How to find the Index of Substring in Swift ?

Answer

✐ Examples

1 Finding the index of "World" in "Hello World"

Swift Program

Output

2 Finding the index of "Prog" in "Swift Programming"

Swift Program

Output

Summary

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