Exploring Range Types in Swift Programming
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Chapter 1: Understanding Ranges in Swift
In Swift, ranges are essential for defining a set of values that lie between a minimum and a maximum limit. They can be utilized for various purposes, such as slicing arrays and checking if a value exists within a specified range.
Types of Ranges
Swift provides several types of ranges for developers to use. The range operator serves as the most straightforward way to interact with these types. Let’s delve into the three primary types of ranges available in Swift.
1. Closed Ranges
The closed range operator, denoted as a…b, includes all values from the lower limit, often referred to as a, to the upper limit, b. For instance, when we refer to "0 to 20, including 20," we mean this.
Here's an example:
let numbers = 0…9
for num in numbers {
print(num)
}
In this code, the … operator is utilized to print each number from 0 to 9 within a for loop. In this instance, numbers is a ClosedRange type, which is a generic type that we have created based on integers. The for loop works with a separate type known as CountableClosedRange, allowing for iteration over this range.
2. Half-Open Ranges
The half-open range operator, indicated by a..b, does not include the upper limit in the range. Therefore, a range defined as 0..<9 excludes 9. Here’s an example:
let numbers = 0..<9
for num in numbers {
print(num)
}
// Output: 0, 1, 2, 3, 4, 5, 6, 7, 8
The half-open range operator creates this effect. You might wonder why we have both operators for seemingly similar purposes. Ending a range one item earlier can be useful, particularly in various scenarios, such as when working with array indices.
3. One-Sided Ranges
Next, we explore one-sided ranges, which differ from closed and half-open ranges by either lacking a lower or upper limit. The operators for one-sided ranges are:
- a…, which includes everything from a to the end.
- …a, which includes everything from the beginning up to a.
- ..a, which includes everything from the start up to a, excluding a.
For example:
let cars = ["Mercedes", "BMW", "Hyundai", "Kia", "JEEP"]
print(cars[2...]) // ["Hyundai", "Kia", "JEEP"]
print(cars[...1]) // ["Mercedes", "BMW"]
print(cars[..<1]) // ["Mercedes"]
Remember, one-sided ranges and slices are constructs that provide a view into a dataset without making a physical copy of the data.
Strings vs. Ranges
Strings in Swift behave differently than simple character arrays found in many programming languages. For instance:
let name = "Rashad"
print(name[0]) // This will not work as expected.
This code fails because Swift uses variable width UTF-8 encoding for strings. As such, you cannot directly access a character by index in the same way. Instead, Swift provides string APIs that work with indices that can be incremented.
Here's how to create indices:
let desc = "Rashad is an innovative iOS Developer"
let start = desc.index(desc.startIndex, offsetBy: 2)
let end = desc.index(desc.startIndex, offsetBy: 3)
print(desc[start..<end]) // Output will be 'sh'
Range-Based Pattern Matching Operator
Another interesting feature of ranges is the ability to use them for pattern matching:
let statusCode = 201
if 200..<300 ~= statusCode {
print("Success")
}
Using the conditional ~= operator allows you to check if a number falls within a specified range. This is functionally similar to using (200..<300).contains(statusCode), but it's more concise and can be used in switch statements for evaluating multiple values.
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Chapter 2: Additional Resources on Range Operators
In this video titled "24 Swift Programming - Closed Range Operator," viewers can learn more about closed range operators in Swift with practical coding examples.
The video "23-Range Operators in iOS Swift | Define the Ranges" offers a comprehensive overview of range operators in Swift, essential for effective programming.