How Can I Efficiently Check for Key Existence Across Multiple Go Maps?

Efficient Key Existence Check in Multiple Maps

In Go, it is common to work with maps, which are efficient data structures for retrieving key-value pairs. However, the developer provided code demonstrates the need to check for the existence of a key in two separate maps. The question remains whether this process can be made more concise.

As explained in the answer, using the special v, ok := m[k] form in Go for checking key existence is limited to single-variable assignments. Therefore, combining the two checks into one if condition using this form is not feasible.

However, there are alternative approaches to achieve the desired functionality:

1. Tuple Assignment:
   If the value type of the map is an interface type and you can ensure that the nil value is not used, you can perform tuple assignment using two index expressions:

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

2. Helper Function:
   A helper function can be created to perform the key existence check in both maps and return the results:

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

   This function can then be used as follows:

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

These approaches allow for a concise and efficient check for the existence of a key in multiple maps within a single conditional statement.

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