Redux Notes

gistfile1.txt

1/ 1 object to represent the whole set of app data
2/ State is read only
3/ Pure functions dont modify arguments and dont rely on anytihng other than arguments passed to them to calculate
4/ UI is a representation of application state,
5/ State changes use pure functions so you take the existing state and the action to calculate a new state from, then pass that back. (testable and predictable). The new state can still reference old objects that made up the previous state if these have not been modified
6/  Reducer function takes the state and action arguments to create new state. (an action is the minimum set of arguments needed to create a new state object from its previous state
7/ If reducer recieved undefined as its stateargument it must return what is to be considered the inital state of the application
8/ If a reducer recieves an unknow action it mus return the existing state
9/ return [...state, {id:action.id, text:action.text}] //this creates a new array using the old arry with the new records appended in
10/ return state.map(todo => { 
	if (todo.id !== action.id){
		return todo;
	} 
	return { ...todo,
	completed: !todo.completed  //spread opperation uses old object as base but completed is overriden and reversed here
	};	
});


User Reducer composition pattern to seperate concerns
combineReducers - a reduc function for automatically combining them
name reducers after the state keys they manage

expect liabary