How Can I Efficiently Check for Key Existence Across Multiple Go Maps in a Single Condition?

Determining Key Existence Across Multiple Maps

When working with multiple maps, it is often necessary to check if a specific key exists in all of them. While the following approach is common:

if v1, ok1 := map1["aaa"]; ok1 {
    ...
}
if v2, ok2 := map2["aaa"]; ok2 {
    ...
}

it involves multiple if statements. Is there a more concise way to perform this check in one condition?

Attempts at Condensing Syntax

One possible solution is to evaluate the key existence in both maps and then check for their intersection:

v1, ok1 := map1["aaa"]
v2, ok2 := map2["aaa"]
if ok1 && ok2 {
    ...
}

However, this approach necessitates assigning and checking in two separate steps.

Limitations of Single-Condition Key Checks

As it turns out, the Go language does not allow for checking multiple key existences in a single if condition. According to the Go specification, an index expression on a map yields an additional boolean value indicating the presence or absence of the key. This special syntax can only be used in assignment or initialization.

Therefore, it is not possible to perform a combined key existence check using just the special v, ok := m[k] form.

Alternatives for Key Existence Checks

If the value type of the map is an interface type and can be guaranteed not to have a nil value, an alternative approach is to use tuple-assignment to check for key existence:

if v1, v2 := m1["aaa"], m2["aaa"]; v1 != nil && v2 != nil {
    ...
}

For more complex cases, a helper function can be created to encapsulate the key existence checking logic:

func idx(m1, m2 map[string]interface{}, k string) (
    v1, v2 interface{}, ok1, ok2 bool) {

    v1, ok1 = m1[k]
    v2, ok2 = m2[k]
    return
}

// Usage example:
if v1, v2, ok1, ok2 := idx(m1, m2, "aaa"); ok1 && ok2 {
    ...
}

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