How Can I Assign a Go Slice of Structs to an Interface Slice?

Interface Slices and Struct Arrays in Go

In Go, assigning a slice of structs ([]MyStruct) to an interface slice ([]interface{}) is not directly possible. This is because structs and interfaces use different memory representations.

Struct fields are contiguous in memory, while interfaces are stored as type information and data pairs. This difference prevents direct conversion between the two.

Why Direct Assignment Fails

The compiler error when attempting to assign x (a slice of structs) to y (an interface slice) reflects this underlying difference. Go requires type compatibility for assignments, and the two types do not match.

Alternatives for Handling Generic Object Arrays

Despite the inability to directly assign struct arrays to interface slices, Go offers several alternative approaches for handling generic object arrays:

1. Copy Elements Individually: Elements of a struct array can be manually copied into an interface slice using a loop.
2. Interface Slices: You can create a slice of interfaces, where each interface holds an individual struct object.
3. Interface Wrapper: An interface wrapper can be defined to represent the struct array type and stored as an interface value.

Example Code

// Copy Elements Individually
var x []MyStruct = [...]MyStruct{{5}, {6}}
var y []interface{}
for _, v := range x {
    y = append(y, v)
}

// Interface Slices
var x []MyStruct = [...]MyStruct{{5}, {6}}
var y []interface{} = make([]interface{}, len(x))
for i, v := range x {
    y[i] = v
}

// Interface Wrapper
type MyStructArrayWrapper interface {
    Get() []MyStruct
}
type MyStructArrayWrapperImpl struct {
    array []MyStruct
}

func (w *MyStructArrayWrapperImpl) Get() []MyStruct {
    return w.array
}
x := []MyStruct{MyStruct{5}, MyStruct{6}}
var y interface{} = &MyStructArrayWrapperImpl{x}

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