Why Can't I Append to Slices in Go Struct Methods Using Value Receivers?

Why Slices Cannot Be Appended to as Properties of GoLang Structs When Using Certain Function Structures

In GoLang, data is passed by value, resulting in a copy of the passed value being created. This behavior affects the ability to append to slices in specific scenarios involving struct methods.

Case Study: Test3

In the example provided, Test3 exhibits this issue due to its combination of value-type receiver in combo() and non-pointer receiver in run(). This setup means that when combo() is called within run(), a copy of c (of type Test3) is created.

Consequences of Value-Type Receiver

The consequence of this approach is that combo() operates on a copy of the c struct, not the original. Since c.all is a field within the copy, any modifications made to it are confined to that copy. When Test3.run() returns c.all, the reported slice is an empty (nil) slice because it refers to a field within the discarded copy of the Test3 struct.

Solution: Pointer Receiver

The solution to this issue lies in using a pointer receiver in combo(). This change ensures that combo() operates on a pointer to a Test3 struct, allowing for modifications to the actual struct.

When Test3.run() calls combo() using a pointer receiver, the changes to c.all are indeed persisted, resulting in the desired output.

Conclusion

Understanding the implications of value and pointer receivers is crucial for effectively utilizing structs and slices in GoLang. This knowledge empowers developers to manipulate data as intended and avoid unexpected behavior.

The above is the detailed content of Why Can't I Append to Slices in Go Struct Methods Using Value Receivers?. For more information, please follow other related articles on the PHP Chinese website!