How to Safely Convert a Slice of Strings to a Slice of a Custom Type in Go?

Conversion of a Slice of String into a Slice of Custom Type

This question arises from an attempt to convert a slice of string ([]string) into a slice of a custom type (Hand), both slices having elements with identical underlying types (Card). The compiler flags this as an error, raising concerns about type compatibility and the need for a workaround.

The underlying issue stems from the Go specification's decision to prohibit direct conversions between slices of different types, even if their elements share the same type. This is intended to prevent inadvertent conversions between unrelated types that happen to have similar structures.

To address this, the safest approach is to copy the elements of the slice. However, if copying is impractical due to potential data modification, there is an alternative using the unsafe package:

unsafe.Pointer(&value)
*(*[]Card)(x)

Where:

• value is the original slice to be converted.
• *unsafe.Pointer(&value) converts the slice's reference (a pointer) to a *[]string to an unsafe.Pointer.
• *(*[]Card)(x) dereferences the unsafe.Pointer and casts the resulting pointer to *[]Card.

This allows the slice to be converted directly without copying. However, it is essential to use this method with caution and recognize the inherent risks associated with bypassing type checking.

There have been discussions within the Go community regarding allowing conversions between recursively equivalent types. However, such a proposal has not been implemented as of yet.

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