Go - Merging 2 functions whose only difference is the arguments type

Question

I have those 2 almost exact functions :

Number 1:

func mergeSlicesOfRequestObjects(aSliceDestination *[]RequestObject, aSliceSource []RequestObject) {
for _, oSliceSourceItem := range aSliceSource {
    // Get current key
    iIndexSourceItemFound := -1
    for iIndexAttribute, oSliceDestinationItem := range *aSliceDestination {
        if oSliceSourceItem.Key == oSliceDestinationItem.Key {
            iIndexSourceItemFound = iIndexAttribute
            break
        }
    }

    // Update attribute
    if iIndexSourceItemFound == -1 {
        *aSliceDestination = append(*aSliceDestination, oSliceSourceItem)
    }
}
}

Number 2:

func mergeSlicesOfResponseObjects(aSliceDestination *[]ResponseObject, aSliceSource []ResponseObject) {
for _, oSliceSourceItem := range aSliceSource {
    // Get current key
    iIndexSourceItemFound := -1
    for iIndexAttribute, oSliceDestinationItem := range *aSliceDestination {
        if oSliceSourceItem.Key == oSliceDestinationItem.Key {
            iIndexSourceItemFound = iIndexAttribute
            break
        }
    }

    // Update attribute
    if iIndexSourceItemFound == -1 {
        *aSliceDestination = append(*aSliceDestination, oSliceSourceItem)
    }
}
}

As you can see the only difference is the struct type of the arguments of the functions.

So here is my question : is there any way to merge those 2 functions into one ?

I've tried using interfaces but I can't figure it out...

Thanks for all the answer in advance :)

Cheers

EDIT

I've implemented thwd answer but I'm getting errors. Here's what I've done:

type Request struct {
    Headers         []RequestObject
}

type RequestObject {
    Key string
}

type Keyer interface {
    GetKey() string
}

func (oRequestObject RequestObject) GetKey() string {
    return oRequestObject.Key
}

func mergeKeyers(aDst *[]Keyer, aSrc []Keyer) {
    // Logic
}

func test() {
    // rDst and rSrc are Request struct
    mergeKeyers(&rDst.Headers, rSrc.Headers)
}

And I'm getting the following errors when executing test():

cannot use &rDst.Headers (type *[]RequestObject) as type *[]Keyer in argument to mergeKeyers
cannot use rSrc.Headers (type []RequestObject) as type []Keyer in argument to mergeKeyers

Any idea why ?

BTW, your [overly verbose variable names](http://research.swtch.com/names) and merge semantics makes it hard to read and you have an O(n×m) algorithm where you could use a [O(n+m) one](https://play.golang.org/p/JGfq_QmtvA). — Dave C, Aug 17 '15 at 21:04
`aSliceDestination *[]RequestObject` should probably be a map in the first place. — kostya, Aug 18 '15 at 01:55

score 4 · Accepted Answer · edited May 23 '17 at 11:58

Define an interface:

type Keyer interface {
    Key() int // or whatever type the Key field has
}

Then implement the interface on both types:

func (r RequestObject) Key() int {
    return r.Key
}

func (r ResponseObject) Key() int {
    return r.Key
}

And rewrite your function to take this interface (and not use hungarian notation and endlessly long variable names):

func mergeKeyers(dst *[]Keyer, src []Keyer) {
    for _, s := range src {
        f := -1
        for i, d := range *dst {
            if s.Key() == d.Key() {
                f = i
                break
            }
        }
        if f == -1 {
            *dst = append(*dst, s)
        }
    }
}

Also, take into account Dave C's comment:

you have an O(n×m) algorithm where you could use a O(n+m) one.

I'll leave it up to you to optimize your code in that way.

Edit to address your second question:

The types *[]RequestObject and *[]Keyer are distinct and not interchangeable. What you need to do is convert your slice of RequestObjects to a slice of Keyers.

This is as easy as iterating over the []RequestObject and assigning each entry to a new entry in a value of type []Keyer.

Go - Merging 2 functions whose only difference is the arguments type

1 Answers1