Export Function in Golang
Overview
In this tutorial, you will learn how to export a golang function that you can use in another package. We will discuss why it is required, why it is a good practice, and when not to use it.
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Why Export a Function?
The basic rule of 101 programming is modularity and reusability. Using modularity, you break down a feature into smaller tasks, and using reusability, you reuse the same functionality at multiple places.
By exporting the function, you can achieve reusability.
In golang, by default the scope of a function is limited to the package it is defined. To access a function in another package, you have to explicitly export it.
In golang, there is no special keyword required to export a function. Golang exports a function if its name's first letter is Uppercase.
Export a Function in Golang
Create a project directory structure as below:
Create an area/area.go file. This file contains a function to calculate the area of a circle.
Create a main.go file. This is the entry point of the program. From here you will try to access areaOfCircle.
Run the program:
You will notice it will throw an error as area.areaOfCircle is undefined.
Now change the function name to uppercase AreaOfCircle.
Run the program:
This time it will run and return the output.
Examples
Exporting using uppercase the first letter is not limited to the function, you can even export a struct and a variable. In short, anything which starts with an uppercase is an export.
Export a Variable
Let's follow the same directory structure and example. We will create a constant variable Pie and print its value in main.go.
Update area.go.
Update main.go
Output:
In this example, we created a constant variable Pie and printed its value in main.go.
Export a Struct
In this example, we will create a Rectangle struct and a function to calculate its area.
Update area.go
Update main.go
Output:
Remember in this example, the name of the struct and its fields', the first letter is in Uppercase.
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Conclusion
In this tutorial, we learned how to export a function to make code reusable. We learned, in golang, there is no special keyword required to export a function. By Uppercasing the first letter of a function it exports.
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