Why Doesn't `fmt.Println()` Call My Stringer Method?

Why My Stringer Interface Method Isn't Invoked When Using fmt.Println()

You have a method String() defined on *Car, but when using fmt.Println(myCar), your object is a value and not a pointer. This behavior is due to fmt.Println() implicitly converting the myCar object to a value of type interface{} and then using a type switch to determine how to print it.

The type switch in the fmt package checks for a case of type fmt.Stringer. However, this check fails because Car (and not *Car) implements the String() method. Calling String() manually works because the compiler automatically converts myCar.String() to (&myCar).String(), supplying the necessary pointer.

To resolve this issue, you have two options:

• Implement String() on Car instead of *Car.
• Always pass a pointer to fmt.Println():

fmt.Println(&myCar)

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