CODEWITHSUNDEEP
gogenerics
JaskeyLam
JaskeyLam

Reputation: 15785

Declare a function parameter with returning value error

I am writing a method to do metrics that can wrap any method. Something like:

func DoAndMonitor(f func() error, simpleKey string) {
    metrics.IncrCounter("activity."+simpleKey+".cnt", 1)
    if err := f(); err != nil {
        metrics.IncrCounter("activity."+simpleKey+".fail", 1)
    } else {
        metrics.IncrCounter("activity."+simpleKey+".fail", 1)
    }
}

This works for some cases. But it is not easy to use, say I have any functions below,

myMethod() (val1 string , val2 string , err error)
myMethod()2 (val string , err error)
myMethod()3 ( err error)
myMethod()4 (val int64,  err error)

When I use myMethod(), I may write something like:

ret1, ret2, err := myMethod()
if err :=nil {
    //log 
    return nil, err;
} else {
    //do something...
    return something,nil
}

But when I use DoAndMonitor, I hope the DoAndMonitor function can return the same type as myMethod like :

ret1, ret2, err := DoAndMonitor(func(){
   return myMethod() 
},"mykey");// this is what i hope, but i can't do this now

if err :=nil {
    //log 
    return nil, err;
} else {
    //do something...
    return something,nil
}

How can I achieve this?

Upvotes: 0

Views: 1077

Answers (1)

Aliics
Aliics

Reputation: 129

The closest you can get to this is by using type parameters and making a few variations of the same function.

func DoAndMonitor(f func() error, simpleKey string) { ... }
func DoAndMonitor1[T any](f func() (T, error), simpleKey string) T {
    x, err := f()
    if err != nil {
        metrics.IncrCounter("activity."+simpleKey+".fail", 1)
    } else {
        metrics.IncrCounter("activity."+simpleKey+".success", 1)
    }
    return x
}
// and so on...

You could then invoke your function like so:

x := DoAndMonitor1[int](func() (int, error) { return 42, nil }, "foo")

A quick playground link to demonstrate this, but with panics instead of your nice metrics. :) https://go.dev/play/p/SMAhUCoIYcj

Upvotes: 1

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