How to Handle Null Values When Parsing JSON int64s in Go?

JSON Parsing of int64s: Handling Null Values in Go

When parsing JSON streams in Go, handling null values can be a challenge, especially when dealing with int64 types. As demonstrated in the example provided, attempting to unmarshal a JSON object containing a null value into a struct field of type int64 will result in an error due to the type mismatch.

Using a Pointer to Address Null Values

A straightforward solution to this issue is to use a pointer to int64. A pointer can be nil, representing a null value, or it can point to a valid int64 instance with an associated value. This approach is supported by Go's JSON package.

type World struct {
    Data *int64
}

By modifying the struct definition above to use a pointer to int64, we can now successfully unmarshal the JSON data without encountering the previous error. The *int64 allows the JSON parser to represent null values as nil pointers.

Mapping null to Non-Null Values

If desired, you can map the null values to a non-null value, such as -1 or MinValue. This can be achieved by custom processing the JSON data after unmarshaling. For example:

func MapNull(data *int64) int64 {
    if data == nil {
        return -1
    }
    return *data
}

By invoking the MapNull function after unmarshaling, you can replace any null values with the desired non-null representation.

Conclusion

Handling null values when parsing JSON data containing int64 types in Go can be achieved by employing a pointer to int64. This technique allows the JSON parser to represent null values and preserves the original data structure. If necessary, custom post-processing can be applied to map null values to alternative non-null representations.

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