In Go: Why do function parameters and return values ​​often use []*User instead of []User?

Detailed explanation of Go language slice: In-depth understanding []*User

Go slicing is powerful, efficient and flexible, and is ideal for many programming tasks. But the slice type []*User often confuses developers. This article will explore the meaning and usage scenarios of []*User in depth, explaining the reasons why it frequently appears in function parameters and return values.

Why is Go slicing a reference type, but []*User is commonly used instead of []User in function parameters and return values?

The key lies in the type of slice elements. var users []*User , whose elements are pointers to the User structure. Each element is a pointer pointing to the User structure instance on the heap. Modifying the slice element will directly modify the corresponding User structure.

The slice declared by var users []User is the User structure itself (value type). The slice stores a copy of the User structure. Modifying the slice element will only modify the copy and will not affect the original User structure.

Therefore, if the function needs to modify the User structure pointed to by the external variable, you must use []*User . []*User ensures that the modifications to slice elements inside the function will be reflected outside the function, while []User can only modify the copy, and external variables are not affected. When modifying multiple User structures, []*User is more efficient, avoiding performance losses of value copying.

This difference is equally important in function parameters and return value transfer. Using []*User as a parameter, the function can directly operate the incoming User structure, and the modification results will be reflected outside the function. Using []User as a parameter, the function can only modify the copy and cannot change the external User structure. Therefore, it is crucial to choose the right slice type and depends on actual needs.

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