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objective c - Need help with application design (MVC, classes etc.)

问题描述:

I'm pretty new to object oriented programming (do have scripting knowledge in PHP and Posix shell programming) and I'm working on a beer recipe application. I've already started the project, but I guess the design is not that good from a MVC point of view. I hope you will help me get the design right. Here are a couple of things to know about the application.

The application needs to be a Document Based Application (open/save recipes in Beer XML). The main window has several textfields to set information like: name, beertype, volume etc. Then there are a couple of tableviews with arrays for: malts, hops and spices, each having their own sheet for adding values.

How should I make my classes? Like this?

  • NSDocument class (with the open/save XML code)
  • (3x) NSWindowController (for each sheet: malts, hops, spices)
  • (3x) NSArrayController (for each tableview: malts, hops, spices)

Should the arrays, managed by the NSArrayController objects, be separate classes (in a MVC perspective (as Model)) or should they be incorporated into their NSArrayController class?

网友答案:

I would start by brushing up on a couple of Apple provided docs:Object-Oriented Programming with Objective-C and Cocoa Fundamentals Guide.

I would also look at using Core Data. With relatively little implementation you have a very powerful data structure (the M in MVC) that is easy to implement with your view and view controllers (the V & C): Core Data Programming Guide

I highly recommend reading these. They are not bad reads and you gain a TON of knowledge. Apple docs are really the best.

Good luck.

网友答案:

Assuming that these are your requirements,

  • Editor application that uses xml (beerxml) as it datasource.
  • Viewer that shows the available data (in a tabular format or as sheets)
  • User can add/remove/edit entries in each xml
  • There exists a relationships between the xmls (datasources) (unsure...)

Before applying any design pattern, you should start applying the basic OOP concepts to identify and create classes (state and behavior) and define the relationship between the classes.

For example, receipes.xml is used to denote the recipes used to manufacture a product. To design a class for this go through the xml. You can identify the following data classes (objects i.e. instances of classes represent a real world entity, while the class is more like a template/blue print for the object):

  • Recipe (main class)
  • Hop
  • Fermentable
  • Yeast
  • Water
  • Style
  • Equipment
  • Mash
  • MashStep and so on.

Once you have identified the classes that form your data model (information repository), identify the properties and behavior of each class. For example, the Yeast class would contain the properties, Name, Version, and so on. Do not worry about the type of the property (string, integer, etc.).

To identify the controllers, view the application from the point of view of the user. What are the use cases (what does the user do with the application? Edit? Add? etc.). These use cases will inadvertently require processing information in a particular flow (sequence). The information is available in your model classes. The controller will invoke operations on the model classes and determine the interaction between them.

For example, suppose there is a use case that the use needs to add a new yeast to the system. Then the controller would create a new instance of the Yeast class and populate it with values supplied by the user (after performing some sort of validation). The created yeast would then be added to the ListOfAvailableYeasts and made available to other classes.

The view is (as the name suggests), a user interface to your data. In MVC, the view is usually updated by an observer that monitors the model for changes and updates the UI accordingly (there are several variation to MVC pattern).

The main point here is that you should first focus on object orientation design first rather than jumping directly into the design patterns.

If you need some guidelines on how to create classes from the xml, then take a look at the xsd.exe tool. You can generate the xsd (xml schema) from an xml and then use this xsd to generate a class hierarchy for the xml (I suggest you start with recipes.xml). You can modify the generated classes to your requirement.

The generated classes would look something like this,

/// <remarks/>
[System.CodeDom.Compiler.GeneratedCodeAttribute("xsd", "2.0.50727.3038")]
[System.SerializableAttribute()]
[System.Diagnostics.DebuggerStepThroughAttribute()]
[System.ComponentModel.DesignerCategoryAttribute("code")]
[System.Xml.Serialization.XmlTypeAttribute(AnonymousType=true)]
public partial class RECIPESRECIPE {

    private string nAMEField;

    private string vERSIONField;

    private string tYPEField;

    private string bREWERField;

    private string aSST_BREWERField;

    private string bATCH_SIZEField;
...
}


Hope that this is sufficient to get you started.

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