Swift Strideable: A Comprehensive Overview and Practical Examples

Swift's Strideable protocol is essential in allowing you to represent values that specific increments or decrements can traverse. When working with sequential values, such as numeric ranges, and needing to control step increments in a loop, the strideable protocol shines.

In this blog, you will understand Swift’s Strideable, how it works, and how to use it to make code both efficient and expressive.

What Is Swift Strideable?

Swift’s Strideable protocol enables types to define strides, meaning they can increment or decrement in value by specified distances. This protocol allows a value to advance or retreat by any defined interval, or stride, giving you fine control over how sequences are traversed. It’s particularly useful in tasks where you want to iterate with flexible step sizes or in custom sequences. The strideable type effectively bridges discrete values with continuous ones, making iteration through ranges straightforward.

1// Simple example of a stride
2let range = stride(from: 0, through: 10, by: 2)
3for value in range {
4    print(value) // Output: 0, 2, 4, 6, 8, 10
5}

​

This stride example shows a sequence of integers that steps through values by a stride of 2, covering the range between 0 and 10. Here, each element is derived by advancing by a distance of 2 from the starting value.

Key Concepts of Strideable in Swift

The strideable protocol defines the fundamental methods and properties needed for a type to be strideable, including its ability to calculate distance and to return advanced values. Let’s explore the primary components.

1. Stride Method

The core functionality of Swift’s strideable protocol revolves around the stride(from:to:by:) and stride(from:through:by:) functions. These methods allow a strideable type to iterate through values by specified increments, moving from a starting value to an end value.

• stride(from:to:by:) - This function iterates to, but does not include, the end value.

• stride(from:through:by:) - This variant includes the end value if the stride aligns perfectly.

Using strideable’s stride method is especially helpful when you want to iterate with custom increments, including a negative stride if you need to decrement.

1// Stride with negative step
2let descendingRange = stride(from: 10, to: 0, by: -2)
3for value in descendingRange {
4    print(value) // Output: 10, 8, 6, 4, 2
5}

​

In this code, a negative stride allows you to decrease from the starting value of 10 towards 0, demonstrating how to use strideable with a negative stride.

2. Distance and Advanced

The strideable protocol defines a method to calculate the distance between two values. This is essential for types representing continuous values, where calculating the distance is necessary for creating flexible ranges. Swift provides two key methods:

• distance(to:) - Calculates the numeric distance to a target value.

• advanced(by:) - Advances (or retreats, if negative) by a specified stride.

Let’s examine these in practice.

1// Distance and advancing with strideable
2let startValue = 0
3let endValue = 10
4let step = 2
5
6let distance = startValue.distance(to: endValue) // Output: 10
7let advancedValue = startValue.advanced(by: step) // Output: 2

​

Here, distance(to:) measures the gap between two values, startValue and endValue, while advanced(by:) moves startValue forward by step.

3. Implementing Custom Strideable Types

While Swift’s standard library provides Int, Float, and Double as strideable types, there may be cases when you need a custom strideable type, especially when dealing with floating point values or other one-dimensional values.

1struct CustomStride: Strideable {
2    var value: Double
3    func distance(to other: CustomStride) -> Double {
4        return other.value - self.value
5    }
6
7    func advanced(by n: Double) -> CustomStride {
8        return CustomStride(value: self.value + n)
9    }
10}

​

With the distance(to:) and advanced(by:) methods implemented, this custom type, CustomStride, conforms to the strideable protocol. Now you can use it to create sequences that progress by precise, floating-point increments.

Practical Examples of Strideable in Swift

Creating an Array of Strides

Using strideable, you can create an array of strides, making it easy to map each value to another operation or function. For instance, generating a range of values and applying transformations to each element through the map function is straightforward.

1let strideArray = Array(stride(from: 0, through: 5, by: 1))
2let squaredValues = strideArray.map { $0 * $0 }
3print(squaredValues) // Output: [0, 1, 4, 9, 16, 25]

​

This example demonstrates how stride can work with map, allowing each value in the sequence to be transformed individually. By combining strideable types with map functions, you can create powerful sequences for many applications.

Calculating Distances with Operators

Swift allows you to use operators with strideable values, such as +, -, and *, enabling concise calculations. For instance, operators let you work efficiently with offsets and measure distances without writing complex formulas.

1let offset = 5.0
2let base = 10.0
3let adjustedValue = base + offset // Output: 15.0

​

Operators help simplify how you measure and offset distances, making the code more readable and efficient, especially when you need to calculate minimum and maximum values along a path.

Iterating Through Values with Custom Steps

Swift’s strideable types allow you to iterate easily through sequences by custom increments. By using custom steps, you can model scenarios such as time intervals, spatial offsets, or even animated paths. For example, a countdown sequence with custom decrement steps can be implemented with stride.

1for value in stride(from: 10, to: 0, by: -1) {
2    print(value) // Output: 10, 9, 8, ..., 1
3}

​

This countdown uses a negative stride to iterate from the starting value of 10 down to the end value of 1.

The Bottom Line!

In summary, Swift Strideable offers incredible flexibility for handling intervals, whether through advanced types, custom strides, or functions like distance, advanced, and map. The strideable protocol simplifies how values are incremented, adjusted, or iterated over, making it a fundamental tool in Swift for working with sequences, one-dimensional values, and advanced range manipulations.

By understanding the core principles and leveraging strideable effectively, you can implement efficient and powerful stride-based sequences in Swift. This versatility makes Swift strideable an essential tool for developers interested in continuous and discrete value manipulation, unlocking numerous applications across various fields.

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