Type Assertion with Function Type Variables
This question seeks to understand how to perform type assertion by passing in a type variable into a function. The goal is to achieve something like the following:
// Pseudocode func myfunction(mystring string, mytype Type) { ... someInterface := translate(mystring) object, ok := someInterface.(mytype) ... // Do other stuff } func main() { // Desired function call myfunction("hello world", map[string]string) }
Proper Function Declaration for Type Assertion
In order to perform the type assertion in the given function, the proper function declaration should use interface{} for the type parameter. This is because interfaces in Go can hold any type value. Here's a corrected version of the function declaration:
func myfunction(v interface{}, expectedType interface{}) bool { return reflect.TypeOf(v) == reflect.TypeOf(expectedType) }
Usage in the Main Function
In the main function, the myfunction can be called by passing in a sample value of the desired type instead of the type itself:
assertNoMatch := myfunction("hello world", map[string]string{}) assertMatch := myfunction("hello world", "stringSample") fmt.Printf("%+v\n", assertNoMatch) // false fmt.Printf("%+v\n", assertMatch) // true
Approach Explained
The approach uses the reflect package to compare the type of the actual value (v) with a sample value of the expected type (expectedType). This allows us to perform dynamic type checks, just as if we were using a switch statement to check the type of mystring and casting it to the desired type explicitly.
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