Go, also known as Golang, is a statically-typed, compiled programming language designed for simplicity and efficiency.

When it comes to working with data structures like slices, maps, and channels, you’ll likely encounter the new() and make() functions. While both are used for memory allocation, they serve distinct purposes.

In this article, we’ll explore the differences between new() and make() in Go and discuss when to use each.

The new() Function

The new() function in Go is a built-in function that allocates memory for a new zeroed value of a specified type and returns a pointer to it. It is primarily used for initializing and obtaining a pointer to a newly allocated zeroed value of a given type, usually for data types like structs.

Here’s a simple example:

package main

import "fmt"

type Person struct {
    Name 	string
    Age  	int
    Gender 	string
}

func main() {
    // Using new() to allocate memory for a Person struct
    p := new(Person)

    // Initializing the fields
    p.Name = "John Doe"
    p.Age = 30
    p.Gender = "Male"

    fmt.Println(p)
}

In this example, new(Person) allocates memory for a new Person struct, and p is a pointer to the newly allocated zeroed value.

The make() Function

On the other hand, the make() function is used for initializing slices, maps, and channels – data structures that require runtime initialization. Unlike new(), make() returns an initialized (non-zeroed) value of a specified type.

Let’s look at an example using a slice:

package main

import "fmt"

func main() {
    // Using make() to create a slice with a specified length and capacity
    s := make([]int, 10, 15)

    // Initializing the elements
    for i := 0; i < 10; i++ {
        s[i] = i + 1
    }

    fmt.Println(s)
}

In this example, make([]int, 10, 15) creates a slice of integers with a length of 10 and a capacity of 15. The make() function ensures that the slice is initialized with non-zero values.

When to Use new() and make() in Go

Use new() for Value Types

When dealing with value types like structs, you can use new() to allocate memory for a new zeroed value. This is suitable for scenarios where you want a pointer to an initialized structure.

p := new(Person)

Use make() for Reference Types:

For slices, maps, and channels, where initialization involves setting up data structures and internal pointers, use make() to create an initialized instance.

s := make([]int, 5, 10)

Pointer vs. Value:

Keep in mind that new() returns a pointer, while make() returns a non-zeroed value. Choose the appropriate method based on whether you need a pointer or an initialized value.

Conclusion

Understanding the distinction between new() and make() in Go is crucial for writing clean and efficient code. By using the right method for the appropriate data types, you can ensure proper memory allocation and initialization in your Go programs.