How Do I Correctly Iterate Over a Slice Pointer in Go?

Error Handling for Slice Pointers in Golang

This issue stems from the inability to range over a pointer to a slice. An error will be thrown when attempting to iterate over a slice pointer, such as in the provided code snippet:

func (c *ClassRepository) populateClassRelationships(classes *[]entities.Class) {
    for i := range classes {  // This line causes the error
        class := classes[i]
        // ...
    }
}

Resolution: Dereference the Pointer

Golang does not automatically dereference slice pointers, which means you must manually dereference the pointer to access the actual slice. To fix the error, dereference the pointer in the range statement:

func (c *ClassRepository) populateClassRelationships(classes *[]entities.Class) {
    for i := range *classes {  // Dereference the pointer here
        class := (*classes)[i]
        // ...
    }
}

Understanding Slice Pointers

Slice pointers in Golang are useful when you need to pass slices to functions without copying the underlying array. This optimization avoids unnecessary memory allocation and overhead.

However, it's important to remember that slice pointers are essentially pointing to slices, not arrays. Therefore, there is no need to use a pointer to a pointer to a slice.

Reference

• [Effective Go: Pointers and Slices](https://go.dev/doc/effective_go#pointers_slices)

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