[Go Concepts]

referenceTypes.go

package main
import "fmt"

func main() {
    slc := []int{1,2}
    adjustSlice(slc)
    fmt.Println(slc)

    map1 := make(map[int]int)
    adjustMap(map1)
    fmt.Println(map1)

    sliceOfMaps := []map[int]int{ map[int]int{1: 10, 2: 20}, map[int]int{3: 30, 4: 40} }
    for _, val := range sliceOfMaps {
        // val here is a COPY of the return value of map[int]int{1: 10, 2: 20} which is a pointer. 
        // setting to it works because go dereferences the copied map pointer automatically
        //
        val[5] = 50
        // vs
        //
        // not sure of the way to take a pointer to a map (let's say the map is nil) and initialize the map through the pointer
        // the original question was trying to do this and yes, all you are doing is taking the copy of the pointer to the map (val)
        // and assigning a new pointer to a new map to it.
        //
        // val = make(map[int]int)
        // val[5] = 50 
    }
    fmt.Println(sliceOfMaps)
}

func adjustSlice(slc []int) {
    // slc is a copied slice header and indexing into a slice header finds the underlying
    // array and allows assignment  
    //
    slc[0] = 12345
    // vs
    //
    // slc = []int { 12345, 2}
    // 
    // takes your slice header which is a copy and assigns a new slice header to it. 
    // now the local variable is not the original slice header, rather it is a new one.
    // so the following assignment has no affect on the source slice header
    
}

func adjustMap(map1 map[int]int) {
    // map1 = map[int]int{1:10}
    //
    // takes the pointer to the map (which is just a copy) and overrides it with a new pointer to a new map
    // vs
    //
    map1[1] = 10
    //
    // takes the pointer to the map (which is just a copy) and dereferences it automatically to set an item in it
}