golang: invalid operation: someVar == “” (mismatched types *string and string)

I was trying to see if a value was empty in a golang script I was writing, when I came across an odd error message:

invalid operation: someVar == "" (mismatched types *string and string)

It turns out that the following code doesn’t return a simple string, but an instance of flag.String

someVar := flag.String("somevar", "", "this is a random flag")

To perform the comparison, you need to use a pointer to it as follows:

if *someVar != "" {
    // Do this
}

Michael is a polyglot software engineer, committed to reducing complexity in systems and making them more predictable. Working with a variety of languages and tools, he shares his technical expertise to audiences all around the world at user groups and conferences. You can follow @mheap on Twitter

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