Using controller for logical operations

For simplicity, your myJournal application persists data in memory. You'll use database operations for permanent data storage later on.

Even though you are not using a database operation, you'll implement the typical Create, Read, Update, and Delete (CRUD) operations for your data. Create the JournalController.swift file in the /Sources/App/Controllers directory:

// Journal controller
import Vapor

final class JournalController {
    
    var entries : Array<Entry> = Array() // [1]
    
    //: Get total number of entries
    func total() -> Int { // [2]
        return entries.count
    }
    //: Create a new journal entry
    func create(_ entry: Entry) -> Entry? { // [3]
        entries.append(entry)
        return entries.last
    }
    //: Read a journal entry
    func read(index: Int) -> Entry? { // [5]
        if let entry = entries.get(index: index) {
            return entry
        } 
        return nil
    }
    //: Update the journal entry
    func update(index: Int, entry: Entry) -> Entry? { // [6]
        if let entry = entries.get(index: index) {
            entries[index] = entry
            return entry
        } 
        return nil
    }
    //: Delete a journal entry
    func delete(index: Int) -> Entry? { // [7]
        if let _ = entries.get(index: index) {
            return entries.remove(at: index)
        } 
        return nil
    }
}

extension Array {
    func get(index: Int) -> Element? { // [4]
        if index >= 0 && index < count {
            return self[index]
        }
        return nil
    }
}

The journalController class performs the following operations:

• Declares an array to hold all the instances of Entry in memory
• Returns the number of entries in the array
• Appends a new Entry item to the array
• Adds a safe get(index:) function to the Array extension that checks for bounds
• Retrieves an Entry item identified by a zero-based index from the array
• Replaces a current item in the array with the supplied Entry item
• Deletes an item from the array

An array in [1] will be used as in memory persistence and holds the references for all Entry instances. The total() method in [2] gives out the total number of entries in the array. In [4], a safe get(index:) function is implemented as an extension to Array. It checks for the given index against the bounds of entries array. The functions in [3], [5],[6] and [7] implement the CRUD operations on the array.