I need to check if the same key exists in two maps:
if v1, ok1 := map1["aaa"]; ok1 {
...
}
if v2, ok2 := map2["aaa"]; ok2 {
...
}
Is it possible to join these two conditions into one? I managed to do something like this:
v1, ok1 := map1["aaa"]
v2, ok2 := map2["aaa"]
if ok1 && ok2 {
...
}
but I'm curious whether it (assigning and checking) can be done in one if condition.
No, it can't be done. Spec: Index expressions:
An index expression on a map a of type
map[K]Vused in an assignment or initialization of the special formv, ok = a[x] v, ok := a[x] var v, ok = a[x]yields an additional untyped boolean value. The value of
okistrueif the keyxis present in the map, and false otherwise.
So you can use the special v, ok := m[k] form only if nothing else gets assigned.
However, if you don't use the zero value of the value type of the map, you can do the check using a simple tuple-assignment; by not using the special form but 2 simple index expressions.
For example if your value type is some interface type (e.g. interface{}), and you know you don't use the nil value, you may do the following:
if v1, v2 := m1["aaa"], m2["aaa"]; v1 != nil && v2 != nil {
fmt.Printf("Both map contains key '%s': %v, %v\n", "aaa", v1, v2)
}
Of course with a helper function, you can do it in one step:
func idx(m1, m2 map[string]interface{}, k string) (
v1, v2 interface{}, ok1, ok2 bool) {
v1, ok1 = m1[k]
v2, ok2 = m2[k]
return
}
Using it:
if v1, v2, ok1, ok2 := idx(m1, m2, "aaa"); ok1 && ok2 {
fmt.Printf("Both map contains key '%s': %v, %v\n", "aaa", v1, v2)
}
Try the examples on the Go Playground.
if v1, v2, ok1, ok2 := idx(m1, m2, "aaa"); ok1 && ok2 { looks like a contributing risk factor for intraocular melanoma. A.k.a. eye cancer.
you could also use variadic parameter(three dots) to check multiple keys :
// check map 1 and map2 is null or not
func checkMap(m1, m2 map[string]interface{}, keys ...string) []bool {
var isExist []bool
for key := range keys {
//checking value from map 1
_, ok := m1[keys[key]]
if ok {
isExist = append(isExist, true) // append for the first time to avoid panic
} else {
isExist = append(isExist, false) // append for the first time to avoid panic
}
// checking value from map2
_, ok = m2[keys[key]]
if ok {
isExist[key] = true
} else {
isExist[key] = false
}
}
return isExist
}
And then you can check your keys in order like this :
result := checkMap(myMap, myMap2, "a", "b", "c", "d", "e", "f", "g")
fmt.Printf("result = %+v\n", result) // print the result
if result[0] {
fmt.Println("key a exist in both map")
}
if result[1] {
fmt.Println("key b exist in both map")
}
