Merge pull request nus-cs2113-AY2324S2#42 from yeozongyao/branch-zong…

…yao-categoriseBooks

Update developer guide

docs/DeveloperGuide.md

@@ -4,9 +4,55 @@
 
 {list here sources of all reused/adapted ideas, code, documentation, and third-party libraries -- include links to the original source as well}
 
+Reference to AB-3 Developer Guide
+* [Source URL](https://se-education.org/addressbook-level3/DeveloperGuide.html#documentation-logging-testing-configuration-dev-ops)
+* Used as template to structure this DeveloperGuide
+* Reference to AB-3 diagrams code
+
+Reference to AB-3 diagrams code
+* [Source URL](https://github.com/se-edu/addressbook-level3/tree/master/docs/diagrams)
+* Used as reference to understand PlantUML syntax
+
+
 ## Design & implementation
 
 {Describe the design and implementation of the product. Use UML diagrams and short code snippets where applicable.}
+### Categorising the different books by their genres
+This functionality enables the categorization of books into distinct groups based on their genres, facilitating better 
+organization and tracking. The implementation of this feature involves interactions across multiple classes within the 
+system. 
+#### Overview
+The process of categorizing books by genre is a multi-step operation that involves the following classes:
+1. `BookDetails`: This class contains methods that handle the categorization of books.
+2. `Book`: Individual book objects are updated with their respective genres directly in this class.
+3. `Parser`: This class is responsible for parsing the input command to extract the specific index and genre.
+
+#### Detailed Workflow
+Below is an example usage:  
+Here’s a step-by-step guide on how the feature works:
+Step 1: The user initiates the process by inputting a command like `set-genre 1 Fantasy`. Here, the `Parser` class plays
+a crucial role as it interprets the command and segregates it into a manageable array. The first part of this array holds 
+the command `set-genre`, which indicates the action to be executed.
+
+Step 2: The second segment of the input string is then further dissected into two components, which are the index (`1`) 
+and the genre (`Fantasy`). This step is essential for identifying the specific book and the genre it needs to be 
+associated with.
+
+Step 3: With the index and genre clearly identified, these parameters are passed to the `setBookGenreByIndex` method 
+within the `BookDetails` class. This method is then responsible for assigning the specified genre to the book located at 
+the given index.
+
+#### Implementation and Rationale
+The decision to involve multiple classes in this operation is driven by the principles of object-oriented programming, 
+which emphasize modularity, encapsulation, and separation of concerns. By distributing responsibilities across different
+classes, the system remains flexible, with each class focusing on a specific aspect of the functionality.
+
+* The `BookDetails` class is central to managing book attributes and behaviors, making it the logical location for methods 
+* that categorize books.
+* The `Book` class represents individual books, and it is here that genre information is ultimately stored, aligning with 
+* the principle that objects should manage their own state.
+* The `Parser` class abstracts the complexity of command interpretation, ensuring that user inputs are correctly understood 
+* and acted upon by the system.
 
 
 ## Product scope