go-type-switch

type switch in Go

tags: learning go programming

content

• we have this code:

func (m *Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
	switch msg := msg.(type) {
	case tea.KeyMsg {
		switch {
		case key.Matches(msg, m.keymap.Cancel):
			return m, CancelMsg
		}
		case key.Matches(msg, someotherkey):
			// do something else
	    }
		default:
			// do something
		}
	}
}

• in this case we have a type switch:
  • switch msg := msg.(type)
• statement like msg.(type) can only be used in a switch statement
  • you can’t do msgType := msg.(type)
  • so the below code is not valid

msgType := msg.(type)  // this is NOT ALLOWED
if msgType != tea.KeyMsg { return m, nil }

• if you wanna do if statement with types, need to do go-type-assertion-1

msgType, ok := msg.(tea.KeyMsg)

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