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MVC + BDSM = MVVM? #CocoaConfBy

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Alexey Demedeckiy @DAlooG iOS Developer

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Agenda Architecture definition Process of development MVC approach Model layer BDSM practices MVVM

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Architecture

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Code is a set of entities that can store and transform data. Code is a set of entities that can store and transform data.

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Design is a set of relationships between entities. Design is a set of relationships between entities.

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Architecture is a set of rules which defines design. Architecture is a set of rules which defines design.

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Architecture is meta design.

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Architecture Quality checklist Simple Constant Predictable

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Big architecture Relationships between classes Roles and contracts Files layout

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Small architecture Code layout Code style

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Process

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Knowledge sharing

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Iterations

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KISS

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Code should not predict changes

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Architecture - should

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Extreme architecture

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Bad architecture

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Bad Sprint 1 Sprint 2 Sprint 3 Design 1 Design 2 Design 3 + + Code Design

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Extreme Sprint 1 Sprint 2 Sprint 3 Design 1 Design 2 Design 3 Code = Design =

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MVC

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Model View Controller View Controller Model update state actions updates commands

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Massive ViewController Controller Network Database Business rules

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Many ViewControllers Controller Network Database Business rules Controller Controller

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Change cost Time cost Number of relationships

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Do not change root. Change leafs.

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Many ViewControllers Controller Network Database Business rules Controller Controller

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Model Layer

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Model of something is description of important parts.

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Model can: hide process details abstract actions hide unneeded data

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Many ViewControllers Controller Network Database Business rules Controller Controller

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Many Models Model Network Database Business rules Model Model

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Changes Soft changes Hard changes

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Model is soft change buffer

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Model View Controller View Controller Model update state actions updates change

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MVC - FIXED!

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BDSM Practices which helps

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Bindings

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Controller binds view to model data. Controller call model actions. Model change it’s data. View hook up changes.

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Data-driven model

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All model actions is -(void) Model data is always valid Model data is formatted for view

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Stateless Controller

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Model data is enough to fill UI Model store intermediate state View can animate from state to state

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Mandatory

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Code review B, D and S Architecture has priority over feature Task can`t be closed without code review.

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BDSM Use bindings for model observations Delegate all process handling to Model Delegate all state handling to Model Keep all code in project consistent.

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MVVM

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Multiple Models Model Network Database Business rules Model Model

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Single model Application Model Network Database Business rules

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Application model has wide interface

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Controller problem

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Application Model Controller Controller Controller

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Each Controller can do anything

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View Model to the rescue!

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Application Model View Model View Model View Model

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View model has thin interface

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View model is Application model adapter for specific controller

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View Controller View Model update state actions updates change

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AM-VM-C-V ?

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VC is a View from Application model perspective

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MVVM = MVC

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Summary

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Abstraction level Ownership chain UIKIT Controller View Model Application Model Service Framework Service Interface

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Example https://github.com/DAloG/Todo-MVVM

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Questions? twitter: @DAlooG e-mail: [email protected]

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