Скачать или смотреть How to Match on a Field of a Struct in Rust

A straightforward guide on matching a field of a struct in Rust, with examples to help you call specific functions based on the value of that field.
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How to Match on a Field of a Struct in Rust

When working with Rust, you may find yourself needing to execute different functions based on certain conditions. One common scenario is matching a field in a struct to call the appropriate function. This can be particularly useful in scenarios such as drawing different shapes based on an enum value.

In this guide, we will explore how to match on a field of a struct in Rust, using a practical coding example to illustrate the concept. Let’s dive into the problem!

The Problem: Drawing Shapes

Consider the following Rust code snippet, which contains an enum for various shapes (Circle, Square, Rectangle) and a struct A that makes use of this enum:

[[See Video to Reveal this Text or Code Snippet]]

The goal here is to create a method draw_shapes in the Plan struct that iterates over the items vector and calls the respective drawing function based on the shape encapsulated in the struct A. However, the question arises about how to perform this matching.

The Solution: Matching the Field

The solution to our matching dilemma is simpler than you might think. You can use the match keyword in Rust to evaluate the value of the field directly. Here’s how you can implement the draw_shapes function:

[[See Video to Reveal this Text or Code Snippet]]

Breakdown of the Code

Method Definition:

We define the method draw_shapes within the Plan implementation. This method does not take any parameters other than a reference to self.

Iterate Through Items:

We use self.items.iter() to create an iterator over the vector of type A.

Matching the Field:

The match statement is used on d.b, where d is a reference to the current item in the iteration. This directly accesses the enum field b of struct A.

Calling Draw Functions:

Depending on the variant of the shape, the corresponding function (draw_circle, draw_square, draw_rectangle) is invoked.

Important Note

One of the beautifully flexible aspects of the match statement is that it can evaluate over any expression, not just simple identifiers. This allows us to match on fields directly, enhancing the functionality and cleanliness of our code.

Conclusion

Matching on a field of a struct in Rust may seem tricky at first, but once you understand how to utilize the match expression effectively, it becomes a powerful tool in your programming arsenal. This pattern is especially useful in scenarios where actions depend on varying conditions, like drawing different shapes, handling different types of data, or responding to user input.

Now you can confidently implement this technique in your Rust applications!

Feel free to reach out with any questions or share your experiences with matching in Rust!