How Do Equality Operators Work When Comparing `interface{}` Values in Go?

Comparing Values of Interface{} Type

In Go, comparing values of type interface{} is a common operation. However, it can lead to confusion when comparing non-trivial types, such as custom structs.

Utilizing Equality Operators

To compare interface{} values, the equality operators == and != are employed. These operators follow specific rules defined in the Go Programming Language Specification:

• Interface values are considered equal if they have the same dynamic type and equal dynamic values, or if both have a nil value.
• For non-interface values of type X and interface values of type T, where X implements T, the values are comparable if X is comparable. They are equal if the dynamic type of the interface value matches X and its dynamic value is equal to the non-interface value.

Comparing Structs and Interfaces

Structs play a significant role in type comparisons. According to the specification:

• Struct values are comparable if all their non-blank fields are comparable.
• Two struct values are equal if their corresponding non-blank fields are equal.

Application in Practice

Consider the following slice of interface{} values: []interface{}{1, "Hello", true}. To search for a specific value, such as 1, one can iterate through the slice and compare each element using the equality operator:

for i := 0; i < len(slice); i++ {
  if slice[i] == 1 {
    // Value found!
    break
  }
}

Conclusion

Comparing values of interface{} type in Go involves understanding the equality rules defined in the language specification. By employing these rules, developers can confidently handle comparisons between interface values, including non-trivial types such as custom structs.

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