在Golang中替换数组结构中的数据

Question

I have 3 struct data (GOLANG) that I call A, B, and C, struct C is result array replace between struct A and B when data is similar or more than 0 then I set all result to struct C using array.

Struct A, B, C {
 TransactionDate  string 
 TotalAmount      string 
 TotalTransaction string 
}

A = [
     {2019-02-01 0 0} 
     {2019-02-02 0 0} 
     {2019-02-03 0 0} 
     {2019-02-04 0 0} 
     {2019-02-05 0 0} 
     {2019-02-06 0 0} 
     {2019-02-07 0 0}
   ]

B = [
     {2019-02-02 1000 2} 
     {2019-02-07 200 3}
    ]

I expect the result is like

C = [
     {2019-02-01 0 0} 
     {2019-02-02 1000 2} 
     {2019-02-03 0 0} 
     {2019-02-04 0 0} 
     {2019-02-05 0 0} 
     {2019-02-06 0 0} 
     {2019-02-07 200 3}
  ]

I try using like this but I can't still like my expected result, can you help me to solve this?

func compareReplace() []C{
 var a []A
 var b []B
 var c []C   
 for i := 0; i < len(a); i++ { 
  if a[i].TransactionDate == b[i].TransactionDate {
        if b[i].TotalTransaction != "0" {
            c = append(c, b[i])
        }
  }
 }

 return c
}

Or we can collaborate at https://play.golang.org/p/H-aaolvSDZt

Answer 1

Your logic assumes that the length of a is always the proper count to conditionally iterate through. The playground that @FatchulAmin shared in a comment on @EdChan answer exposed the issue when a is larger than b or vice versa, you will get the "index out of range" error because the smaller slice will no longer have indexes to match the larger. a[i].TransactionDate == b[i].TransactionDate

For sanity, in this case, you should do a check to find the smallest count to iterate with, however, this will not allow you to completely check all of the largest slice.

I suggest merging the slices then finding the largest and smallest to range and loop to remove what you want from the merged. NOTE: @EdChan is right to use one struct since they are all the same.

type FooBar struct {
    TransactionDate  string
    TotalAmount      string
    TotalTransaction string
}

type FooBarSlice []FooBar // this is used as a receiver on func Remove

func compareReplace(a []FooBar, b []FooBar) []FooBar {
    var c FooBarSlice
    c = append(a, b...)


    var largerSlice []FooBar
    var smallerSlice []FooBar
    if len(a) <= len(b) {
        largerSlice = b
        smallerSlice = a
    } else {
        largerSlice = a
        smallerSlice = b
    }

    for _, v := range smallerSlice {

        for j := 0; j < len(largerSlice); j++ {
            if largerSlice[j].TransactionDate == v.TransactionDate && largerSlice[j].TotalTransaction == "0" {

                c.Remove(j)

            }
        }
    }

    return c
}

Full working example: https://play.golang.org/p/iyUYtXlDG54