Angular and the Single Immutable State Tree

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Hallo

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UI Model {…} APPLICATION STATE MANAGEMENT ? sync

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BIDIRECTIONAL (two way) data binding

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UNIDIRECTIONAL data flow

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Redux

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single IMMUTABLE the STATE tree &

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Ciro Nunes FRONTEND ENGINEER @cironunesdev

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Belo Horizonte

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AGENDA

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1. Problems with mutable objects AGENDA

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1. Problems with mutable objects 2. Using immutable objects AGENDA

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1. Problems with mutable objects 2. Using immutable objects 3. The single immutable state tree AGENDA

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MUTABLE OBJECTS make TRACKING hard CHANGES

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@Component({+ ++selector:+'my3person',+ ++template:+`+ +++{{+person.name+}}+lives+at+{{+address.street+}},+{{+address.city+}}+ ++`+ })+ export+class+MyPerson+{+ ++@Input()+person:+{+name:+string+};+ ++@Input()+address:+{+city:+string,+street:+string+}+ } my-person.component.ts

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@Component({+ ++template:+`+ +++{{+person.name+}}+lives+at+{{+address.street+}},+{{+address.city+}}+{{+zipCode+}}+ ++`+ })+ export+class+MyPerson+{+ ++@Input()+person:+{+name:+string+};+ ++@Input()+address:+{+city:+string,+street:+string+};+ ++zipCode:+number;+ ++ngOnChanges(inputChanges)+{+ ++++if+(inputChanges.address)+{+ ++++++this.zipCode+=+this.zipCodes(this.address);+ ++++}+ ++}+ } my-greeting.component.ts

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PROBLEMS WITH MUTABLE OBJECTS

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1. Other components can change it not propagating the change PROBLEMS WITH MUTABLE OBJECTS

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MUTABLE OBJECTS can LEAD issues PERFORMANCE to

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@Component({+ ++selector:+'my3person',+ ++template:+`+ +++{{+person.name+}}+lives+at+{{+address.street+}},+{{+address.city+}}+{{+zipCode+}}+ ++`+ })+ export+class+MyPerson+{+ ++@Input()+person:+{+name:+string+};+ ++@Input()+address:+{+city:+string,+street:+string+};+ ++zipCode:+number;+ ++ngOnChanges(inputChanges)+{+ ++++if+(inputChanges.address)+{+ ++++++this.zipCode+=+this.zipCodes(this.address);+ ++++}+ ++}+ } my-greeting.component.ts

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1. Other components can change it not propagating the change PROBLEMS WITH MUTABLE OBJECTS

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1. Other components can change it not propagating the change PROBLEMS WITH MUTABLE OBJECTS 2. The framework needs to be conservative

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IMMUTABLE OBJECTS win THE for

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IMMUTABLE OBJECTS references NEW creates

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let+person+=+Immutable.Map({+ ++name:+'Ciro',+ ++address:+{+ ++++street:+'Gardenia',+ ++++city:+'Belo+Horizonte'+ ++}+ });+ function+changeAddressStreet(person,+newStreet)+{+ ++return+person.setIn(['address'],+{+ ++++street:+newStreet,+ ++++city:+person.toJS().address.city+ ++});+ }+ let+newAddress+=+changeAddressStreet(person,+'New+Address'); pure-function—sample.ts

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ADVANTAGES OF IMMUTABLE OBJECTS

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1. Tracking changes made easy ADVANTAGES OF IMMUTABLE OBJECTS

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App Todos MyGreeting Todo Todo • person • address • zipcode

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my-person.component.ts @Component({+ ++selector:+'my3person',+ ++template:+`+ +++{{+person.name+}}+lives+at+{{+address.street+}},+{{+address.city+}}+{{+zipcode+}}+ ++`,+ ++changeDetection:+ChangeDetectionStrategy.OnPush+ })+ export+class+MyPerson+{+ ++@Input()+person:+{+name:+string+};+ ++@Input()+address:+{+city:+string,+street:+string+}+ ++zipCode:+number;+ ++ngOnChanges(inputChanges)+{+ ++++if+(inputChanges.address)+{+ ++++++this.zipCode+=+this.zipCodes(this.address);+ ++++}+ ++}+ }

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1. Tracking changes made easy ADVANTAGES OF IMMUTABLE OBJECTS

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1. Tracking changes made easy ADVANTAGES OF IMMUTABLE OBJECTS 2. Able to skip checks, results in better performance

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single IMMUTABLE the STATE tree &

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Redux

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THE SINGLE IMMUTABLE STATE TREE

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1. Unidirectional data flow THE SINGLE IMMUTABLE STATE TREE

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1. Unidirectional data flow THE SINGLE IMMUTABLE STATE TREE 2. Changes are made using pure functions (reducers)

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Actions Reducers Store View REDUX UNIDIRECTIONAL  DATA FLOW subscribe dispatch

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Actions Reducers Store View REDUX UNIDIRECTIONAL  DATA FLOW JS objects subscribe dispatch

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Actions Reducers Store View REDUX UNIDIRECTIONAL  DATA FLOW JS objects subscribe dispatch

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Actions Reducers Store View REDUX UNIDIRECTIONAL  DATA FLOW JS objects Pure functions subscribe dispatch

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1. Always produce the same output given the same input PURE FUNCTIONS 2. Don’t produce side-effects (e.g: mutate state)

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const+initialState+=+{+ ++todos:+[],+ ++currentFilter:+'SHOW_ALL'+ };+ function+rootReducer(state+=+initialState,+action)+{+ ++switch+(action.type)+{+ ++++case+'ADD_TODO':++ ++++++++return+{+ ++++++++++todos:+[...todos,+newTodo],+ ++++++++++currentFilter:+state.currentFilter+ ++++++++}+ ++++++++break;+ ++++default:++ ++++++return+state;+ ++}+ }; root-reducer.ts

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const+initialState+=+{+ ++todos:+[],+ ++currentFilter:+'SHOW_ALL'+ };+ function+rootReducer(state+=+initialState,+action)+{+ ++switch+(action.type)+{+ ++++case+'ADD_TODO':++ ++++++++return+{+ ++++++++++todos:+[...todos,+newTodo],+ ++++++++++currentFilter:+state.currentFilter+ ++++++++};+ ++++++++break;+ ++++default:++ ++++++return+state;+ ++}+ }; root-reducer.ts

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Actions Reducers Store View REDUX UNIDIRECTIONAL  DATA FLOW JS objects Pure functions subscribe dispatch

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Actions Reducers Store View REDUX UNIDIRECTIONAL  DATA FLOW JS objects Pure functions Application state subscribe dispatch

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import+{createStore}+from+'redux';+ import+{rootReducer}+from+'./root3reducer';+ const+appStore+=+createStore(rootReducer);+ appStore.subscribe(callback);+ appStore.dispatch(action);+ appStore.getState(); app-store.ts

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import+{createStore}+from+'redux';+ import+{rootReducer}+from+'./root3reducer';+ import+{Actions}+from+'./actions';+ const+appStore+=+createStore(rootReducer);+ bootstrap(App,+[+ ++provide('AppStore',+{useValue:+appStore}),+ ++Actions+ ]); app-store.ts

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OTHER OPTIONS TO REDUX

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1. ngrx/@store OTHER OPTIONS TO REDUX

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1. ngrx/@store OTHER OPTIONS TO REDUX 2. Victor Savkin’s implementation using observables

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IN SUMMARY

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Mutable objects are bad for modelling application state IN SUMMARY

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Mutable objects are bad for modelling application state IN SUMMARY Immutable objects makes it easy to track changes

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Mutable objects are bad for modelling application state IN SUMMARY Immutable objects makes it easy to track changes Angular 2 CD mechanism makes it even faster

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Mutable objects are bad for modelling application state IN SUMMARY Immutable objects makes it easy to track changes Angular 2 CD mechanism makes it even faster Redux is awesome, but there are other great options