How to Efficiently Copy Data from One Struct to a Nested Struct in Go

Learn step-by-step how to copy data from a flat struct to a nested struct in Go with a practical example. Perfect for beginners and intermediate Go developers!
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How to Efficiently Copy Data from One Struct to a Nested Struct in Go

When working on Go applications, especially when interacting with APIs or automation tools, you may come across situations where you need to transfer data between structs. One common scenario is copying data from a simple struct to a more complex nested struct that has the same fields. In this guide, we'll walk through how to accomplish this using a practical example related to automating story creation in JIRA.

The Problem

Imagine you have a JSON input, representing a JIRA story, that you need to map into Go structs for further processing. Your JSON might look something like this:

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

You've already mapped this JSON into a Go struct called InputJson, but now you need to copy its values into another nested struct called JiraCreateStory. This nested struct has the same fields but organized within additional layers.

Let’s break this down into manageable steps to facilitate the copying of data.

Step 1: Define Your Structs

Before we can copy the data, we need to define the destination struct properly. Here’s how the JiraCreateStory struct is defined:

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

In this structure:

The Fields struct contains the essential attributes needed to create a JIRA story.

Sub-structs (like Project, Assignee, and Issuetype) are used to hold more specific data.

Step 2: Create Your JiraCreateStory Instance

Now that your structs are defined, the next step is to populate the JiraCreateStory with data from the InputJson.

Using a composite literal, construct a JiraCreateStory instance as follows:

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

In this code:

Each field from src (which refers to your InputJson struct instance) is mapped to the respective nested struct in JiraCreateStory.

This composite literal syntax allows for direct initialization with the values stored in your source struct.

Conclusion

Copying data from a simple struct to a nested struct in Go can seem daunting at first, especially with nested data structures. However, with an understanding of how to define your structs and how to use composite literals, this task becomes straightforward.

This structured approach not only helps in maintaining clarity but also aids in better organization of data, making your code more modular and easier to manage in the long run.

Feel free to use the provided examples to adapt to your specific needs within your Go applications!