How to Safely Convert a Go Slice of Strings to a Slice of String Pointers?

Converting a Slice of Strings to a Slice of Pointers to Strings

Problem

You aim to transform a slice of strings into a corresponding slice of pointers to strings. However, your initial approach using a simple loop to copy references encounters unanticipated behavior. You've realized that the loop variable remains as a string, not a pointer, and you wonder how its value can change if it's not a pointer.

Solution: Using Loop Indices

One effective solution involves utilizing loop indices instead of the loop variable to access and append the correct addresses. By iterating through the range of the slice indices, you can access each element in the original slice and obtain its address to insert into the slice of pointers.

Example:

values1 := []string{"a", "b", "c"}
var values2 []*string
for i, _ := range values1 {
    values2 = append(values2, &values1[i])
}

Alternative Solution: Local Variables

Another method involves creating temporary local variables within the loop. These variables will hold copies of each string, and their addresses will be added to the slice of pointers.

Example:

for _, v := range values1 {
    v2 := v
    values2 = append(values2, &v2)
}

Considerations: Memory Management and Modifiability

It's crucial to note that both solutions involve implications for memory management and data modifiability:

• The first solution does not create any additional references, so when the original slice loses its reference, the backing array of strings may be garbage collected. Additionally, any modifications to the strings in the original slice will reflect in the slice of pointers.
• The second solution creates additional local variables and thus references, which can potentially prolong the life of the original slice. However, changes made to the strings in the original slice will not be reflected in the slice of pointers.

Conclusion

By understanding loop variables and addressing memory management and modifiability considerations, you can effectively convert slices of strings to slices of pointers to strings in Golang.

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