Readings: Introductions to React and Components

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Component-Based Architecture
What is Props and How to Use it in React

Component-Based Architecture

1. What is a “component”?
   • A component is a modular, portable, replaceable, and reusable set of well-defined functionality that encapsulates its implementation and exporting it as a higher-level interface.
     A component is a software object, intended to interact with other components, encapsulating certain functionality or a set of functionalities. It has an obviously defined interface and conforms to a recommended behavior common to all components within an architecture.
     A software component can be defined as a unit of composition with a contractually specified interface and explicit context dependencies only. That is, a software component can be deployed independently and is subject to composition by third parties.
2. What are the characteristics of a component?
   • Reusability Components are usually designed to be reused in different situations in different applications. However, some components may be designed for a specific task.
   • Replaceable Components may be freely substituted with other similar components.
   • Not context specific Components are designed to operate in different environments and contexts.
   • Extensible A component can be extended from existing components to provide new behavior.
   • Encapsulated A component depicts the interfaces, which allow the caller to use its functionality, and do not expose details of the internal processes or any internal variables or state.
   • Independent Components are designed to have minimal dependencies on other components.
3. What are the advantages of using component-based architecture?
   • Ease of deployment As new compatible versions become available, it is easier to replace existing versions with no impact on the other components or the system as a whole.
   • Reduced cost The use of third-party components allows you to spread the cost of development and maintenance.
   • Ease of development Components implement well-known interfaces to provide defined functionality, allowing development without impacting other parts of the system.
   • Reusable The use of reusable components means that they can be used to spread the development and maintenance cost across several applications or systems.
   • Modification of technical complexity A component modifies the complexity through the use of a component container and its services.
   • Reliability The overall system reliability increases since the reliability of each individual component enhances the reliability of the whole system via reuse.
   • System maintenance and evolution Easy to change and update the implementation without affecting the rest of the system.
   • Independent Independency and flexible connectivity of components. Independent development of components by different group in parallel. Productivity for the software development and future software development.

What is Props and How to Use it in React

1. What is “props” short for?
   • Properties
2. How are props used in React?
   • Passing data from one component to another.
3. What is the flow of props?
   • Firstly, define an attribute and its value(data)
     • We can define our own attributes & assign values with interpolation { }:

   <ChildComponent someAttribute={value} anotherAttribute={value}/>
   

   • Then pass it to child component(s) by using Props
     • Arguments passed to a function:

     const addition = (firstNum, secondNum) => {  
     return firstNum + secondNum; 
     };
     

     • Arguments passed to a React component:

     const ChildComponent = (props) => {  
     return <p>I'm the 1st child!</p>; 
     };
     

   • Finally, render the Props Data
     • Render a text property with an interpolation:

     const ChildComponent = (props) => {  
     return <p>{props.text}</p>; 
     };
     

     class ParentComponent extends Component {  
       render() {
         return (
           <h1>
             I'm the parent component.
             <ChildComponent text={"I'm the 1st child"} />
             <ChildComponent text={"I'm the 2nd child"} />
             <ChildComponent text={"I'm the 3rd child"} />
           </h1>
         );
       }
     }
     

4. RECAP
   • Props stand for properties and is a special keyword in React
   • Props are being passed to components like function arguments
   • Props can only be passed to components in one way (parent to child)
   • Props data is immutable (read-only)

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