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Go Language Go Language Overview Custom Types Interfaces

Posted by Joey Bryan
Joey Bryan
1,468 Points

I think there may be an issue with the type but I'm really not sure the error is terribly vague.

I feel like there may be an issue with declaring different types for this. I'm a little unclear if they should be strings or ints based on the other packages. Overall not sure where to go from here.

src/schedule/schedule.go 
package schedule

// DECLARE A Displayable INTERFACE HERE
type Displayable interface {
  Display()
}

// DECLARE A Print FUNCTION HERE
func Print(d Displayable) string {
  return d.Display()
}
src/clock/clock.go 
package clock

import "fmt"

type Clock struct {
  Hours int
  Minutes int
}

func (c Clock) Display() {
  fmt.Printf("%02d:%02d", c.Hours, c.Minutes)
}
src/calendar/calendar.go 
package calendar

import "fmt"

type Calendar struct {
  Year int
  Month int
  Day int
}

func (c Calendar) Display() {
  fmt.Printf("%04d-%02d-%02d", c.Year, c.Month, c.Day)
}

1 Answer

Robert Stefanic
Robert Stefanic
35,170 Points
Robert Stefanic
Robert Stefanic
35,170 Points

The types fine and working as expected. The methods of Display() on Clock and Calendar don't return a string, so why would your interface return a string? The Display() methods just print something to the screen, so there's no need for the Print() to return anything because it calls Display(), which doesn't return anything.

Modify your Print() function so that it doesn't return anything.