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Learning from Open Source: Input and output container #87

onmyway133 opened this Issue Oct 17, 2017 · 1 comment


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onmyway133 commented Oct 17, 2017

This is a very nifty trick from ios-oss which was built around MVVM pattern. It uses protocol to define input and output, and a container protocol to contain them. Take for example

public protocol LoginViewModelInputs {


public protocol LoginViewModelOutputs {


public protocol LoginViewModelType {
  var inputs: LoginViewModelInputs { get }
  var outputs: LoginViewModelOutputs { get }

public final class LoginViewModel: LoginViewModelType, LoginViewModelInputs, LoginViewModelOutputs {
  public var inputs: LoginViewModelInputs { return self }
  public var outputs: LoginViewModelOutputs { return self }

Look how LoginViewModel conforms to 3 protocols. And when you access its input or output properties, you are constrained to only LoginViewModelInputs and LoginViewModelOutputs


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MarcSteven commented Jan 8, 2018

Great blog

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