How to assign a default fallback value to a variable

Question content

There is a struct pointer

in my application

type body struct {
   a *string
   b *string
}

I want to pass the values ​​of a and b in body to the function, so that if the pointer a is empty, the default is passed Empty string value. Something like this:

sampleFunc(ctx,*A||"");

func sampleFunc(ctx Context,count string){
// ......
}

what should I do?

Correct answer

Declare a function for calculating a value from a pointer with your desired logic. I'm using generics here so the function works with any type.

// value returns the value the value pointed
// to by p or the empty value when p is nil.
func value[t any](p *t) t {
    var result t
    if p != nil {
        result = *p
    }
    return result
}

Use like this:

samplefunc(ctx, value(a))

APIs with *string fields usually provide helper functions for this purpose. For example, AWS API provides stringvalue function:

sampleFunc(ctx, aws.StringValue(A))

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