Exact-match comparisons in Go use == only when both operands are comparable. The operator compares values according to their types and fields, so equal struct fields can produce true, while a struct containing a slice cannot be compared. section 3.13
Avoid the common mistake of applying == to every value:
- Booleans, numerics, strings, channels, pointers, interfaces, arrays, and structs composed of comparable types support ==. section 3.13
- Slices and maps are not comparable; a struct containing one fails at compile time. section 3.13
- An interface comparison can panic when its dynamic value is an uncomparable type, even though the interface variables themselves are valid. section 3.13
Choose a comparison deliberately
Two customer values containing only an id can be compared with ==. After adding an operations slice, use reflect.DeepEqual for a general deep comparison or write an equal method that compares the id, lengths, and elements explicitly. section 3.13
func (a customer) equal(b customer) bool {
if a.id != b.id { #1
return false
}
if len(a.operations) != len(b.operations) { #2
return false
}
for i := 0; i < len(a.operations); i++ { #3
if a.operations[i] != b.operations[i] {
return false
}
}
return true
}
Inspect an explicit customer comparison that checks fields, slice lengths, and corresponding elements. section 3.13
