I have a question regarding efficiency. I am writing an app for windows phone 7 and care a lot about memory, as I am using extremely long lists.
My question is, what is the size of a class that apart from using normal properties like int, string etc, has also a static int property and an accessor property for the forementioned static field? I need to use a static field, but cannot access it using databinding, thus my question.
An example:
private static int _property1;
public int Property1
{
get { return _property1; }
}
public int property2;
public int property3;
I would be really grateful for your answers.
Here you have static field _property1, which will be shared between all the instances of class, means it will create only one copy of _property1, if someone changes the value of static field it will reflect to every place. So it will increase the efficiency regardless you need to restrict the other users to set/reset static variables..
Related
What is the use of constructor here ?
This is script A :
[SerializeField]
private LobbyFunction _lobbyFunction;
public LobbyFunction LobbyFunction
{
get { return _lobbyFunction; }
}
This is script B:
private void Start()
{
GameObject lobbyCanvasGO = CanvasManager.Instance.LobbyFunction.gameObject;
if (lobbyCanvasGO == null) return;
}
what if I choose not to use the encapsulation ? no error , I guess .Any help would be greatly appreciated ,thanks!
edit: I guess using encapsulation here make the var read- only , only get... and therefore increase the security , people from outside can't change the value ,is it the ans?
This is no constructor but a Property
A property is a member that provides a flexible mechanism to read, write, or compute the value of a private field. Properties can be used as if they are public data members, but they are actually special methods called accessors. This enables data to be accessed easily and still helps promote the safety and flexibility of methods.
In your case it is for granting Read-Only access to the private backing field _lobbyFunction so no other class can change its value since only the class "A" containing _lobbyFunction itself is allowed to assign it.
Btw the way you have it it is equivalent to simply write
public LobbyFunction LobbyFunction { get; private set; }
without the need for a backing field. Then still only the containing class "A" itself is allowed to assign a value while everyone else can read it.
Should I rather create a public static class or use internal constants?
I am working on a very large application and noticed the use of const string at numerous places.This is used to compare the users selection
const string Thatch = "Thatch";
const string BrickAndTimberFrame= "Brick And Timber Frame";
const string OtherRoof = "Other";
etc......
etc......
What I want to do is to rather create public static class in the Core Application (see code below). The reason for this is that I only have to change/add a value at one place only.
public static class RoofConstruction
{
public static String Thatch{ get { return "Thatch"; } }
public static String BrickAndTimberFrame { get { return "Brick And Timber Frame"; } }
etc....
etc....
}
The compare function will then look like this
internal bool SlateTileOrConcreteRoof()
{
return RiskInformation.RoofConstruction.Value == RoofConstruction.Slate ||
RiskInformation.RoofConstruction == RoofConstruction.TileAndSlate ||
RiskInformation.RoofConstruction == RoofConstruction.Concrete;
}
Please add any comments/improvements etc
Generally speaking, I think that “the defining characteristic of ‘a Good Class™’,” is that “it does the right thing, nevermind(!) ‘how, exactly,” it does it.”
When you export constants from the class, this suggests that an unknown-number of other sections of the application (present and future ...) will contain logic that tests against that string.
Therefore, the question that only you can really answer: “do they really care about ‘the value of that string,’ or do they want ‘the answer to a yes-or-no question, which is answered in part based on the value of that string?’” This might guide your decision about what is best to do. (Mind you, I do not think that there is any sort of bright-line rule. I have done it both ways...)
Lets say i have a class to calculate tax. Which is the best practice to design the calcTax method. Option 1 or Option 2. The object pertains to a person and that is why we are storing age and income. I can see the pros and cons of each but just wanted to see if there is a best practice or if one of the two options has a code smell.
Option 1:
class CalcTax
{
private int Age;
private double Income;
public void Update(int age, double inc)
{
Age = age;
Income = inc;
}
public double calcTax()
{
return Age * Income * 0.25;
}
}
CalcTax obj = new CalcTax();
obj.update(5,500)
obj.CalcTax();
Option 2:
class CalcTax
{
public double calcTax(int age, int inc)
{
return age * inc* 0.25;
}
}
CalcTax obj = new CalcTax();
obj.calcTax(10,100);
Could go either way. Depends on what the object is supposed to represent.
If it there is one object for one person (I'm assuming Age and Income relate to a person), and that object is going to be doing a variety of things beyond the one calculation you show, then the fundamental attributes of that person (Age, Income, etc.) should be class attributes. These would likely be set as parameters to new() or perhaps set shortly after the instance was created.
If, however, this is just a calculator object, to be used to process requests for a variety of people, then there is no need to have Age and Income as class attributes at all. You could delete them your Option 2 example entirely, and just have them in the parameters to calcTax().
It probably ends there, with one of those options best matching your project. But if you're creating more of a library function that other programmers will be using in different ways in different projects, you could straddle the fence a bit...
Take Age and Income as parameters to new() and save them as class attributes. Then, make the parameters to calcTax() optional, and default to the class attributes if none are provided. That way, your developers can take whichever approach suits their needs best, and you've got a single codebase to support them both.
As the first comment says, the choice is yours. Try to think about what role your class will play. Is it just a collection of common math functions that you may want to call. If so, then methods with passable parameters are great.
However, if you're generating a tax class that will be specific to a certain context, then maybe something like the below would be best for you. The example below requires the Age and Income and offers up the CalculatedTax as a read-only property.
public class Tax
{
public Tax(int Age, int Income) //constructor, class can not be instantiated without these values
{
this.Age = Age;
this.Income = Income;
}
public int Age { get; set; }
public int Income { get; set; }
public double CalculatedTax //read only property
{
get { return double.Parse((Age * Income).ToString()) * 0.25f; }
}
}
Tax tax = new Tax(5, 1000);
double calculatedTax = tax.CalculatedTax; //1250
One benefit to the above example is that Age and Income are required to generate the CalculatedTax value. By forcing these parameters to be entered in the constructor you make sure they exist, otherwise (for this example) if these were your only three properties, what would be the point of making a class if you weren't going to include one of the required parameters.
Does anyone know the best way to refactor a God-object?
Its not as simple as breaking it into a number of smaller classes, because there is a high method coupling. If I pull out one method, i usually end up pulling every other method out.
It's like Jenga. You will need patience and a steady hand, otherwise you have to recreate everything from scratch. Which is not bad, per se - sometimes one needs to throw away code.
Other advice:
Think before pulling out methods: on what data does this method operate? What responsibility does it have?
Try to maintain the interface of the god class at first and delegate calls to the new extracted classes. In the end the god class should be a pure facade without own logic. Then you can keep it for convenience or throw it away and start to use the new classes only
Unit Tests help: write tests for each method before extracting it to assure you don't break functionality
I assume "God Object" means a huge class (measured in lines of code).
The basic idea is to extract parts of its functions into other classes.
In order to find those you can look for
fields/parameters that often get used together. They might move together into a new class
methods (or parts of methods) that use only a small subset of the fields in the class, the might move into a class containing just those field.
primitive types (int, String, boolean). They often are really value objects before their coming out. Once they are value object, they often attract methods.
look at the usage of the god object. Are there different methods used by different clients? Those might go in separate interfaces. Those intefaces might in turn have separate implementations.
For actually doing these changes you should have some infrastructure and tools at your command:
Tests: Have a (possibly generated) exhaustive set of tests ready that you can run often. Be extremely careful with changes you do without tests. I do those, but limit them to things like extract method, which I can do completely with a single IDE action.
Version Control: You want to have a version control that allows you to commit every 2 minutes, without really slowing you down. SVN doesn't really work. Git does.
Mikado Method: The idea of the Mikado Method is to try a change. If it works great. If not take note what is breaking, add them as dependency to the change you started with. Rollback you changes. In the resulting graph, repeat the process with a node that has no dependencies yet. http://mikadomethod.wordpress.com/book/
According to the book "Object Oriented Metrics in Practice" by Lanza and Marinescu, The God Class design flaw refers to classes that tend to centralize the intelligence of the system. A God Class performs too much work on its own, delegating only minor details to a set of trivial classes and using the data from other classes.
The detection of a God Class is based on three main characteristics:
They heavily access data of other simpler classes, either directly or using accessor methods.
They are large and complex
They have a lot of non-communicative behavior i.e., there is a low
cohesion between the methods belonging to that class.
Refactoring a God Class is a complex task, as this disharmony is often a cumulative effect of other disharmonies that occur at the method level. Therefore, performing such a refactoring requires additional and more fine-grained information about the methods of the class, and sometimes even about its inheritance context. A first approach is to identify clusters of methods and attributes that are tied together and to extract these islands into separate classes.
Split Up God Class method from the book "Object-Oriented Reengineering Patterns" proposes to incrementally redistribute the responsibilities of the God Class either to its collaborating classes or to new classes that are pulled out of the God Class.
The book "Working Effectively with Legacy Code" presents some techniques such as Sprout Method, Sprout Class, Wrap Method to be able to test the legacy systems that can be used to support the refactoring of God Classes.
What I would do, is to sub-group methods in the God Class which utilize the same class properties as inputs or outputs. After that, I would split the class into sub-classes, where each sub-class will hold the methods in a sub-group, and the properties which these methods utilize.
That way, each new class will be smaller and more coherent (meaning that all their methods will work on similar class properties). Moreover, there will be less dependency for each new class we generated. After that, we can further reduce those dependencies since we can now understand the code better.
In general, I would say that there are a couple of different methods according to the situation at hand. As an example, let's say that you have a god class named "LoginManager" that validates user information, updates "OnlineUserService" so the user is added to the online user list, and returns login-specific data (such as Welcome screen and one time offers)to the client.
So your class will look something like this:
import java.util.ArrayList;
import java.util.List;
public class LoginManager {
public void handleLogin(String hashedUserId, String hashedUserPassword){
String userId = decryptHashedString(hashedUserId);
String userPassword = decryptHashedString(hashedUserPassword);
if(!validateUser(userId, userPassword)){ return; }
updateOnlineUserService(userId);
sendCustomizedLoginMessage(userId);
sendOneTimeOffer(userId);
}
public String decryptHashedString(String hashedString){
String userId = "";
//TODO Decrypt hashed string for 150 lines of code...
return userId;
}
public boolean validateUser(String userId, String userPassword){
//validate for 100 lines of code...
List<String> userIdList = getUserIdList();
if(!isUserIdValid(userId,userIdList)){return false;}
if(!isPasswordCorrect(userId,userPassword)){return false;}
return true;
}
private List<String> getUserIdList() {
List<String> userIdList = new ArrayList<>();
//TODO: Add implementation details
return userIdList;
}
private boolean isPasswordCorrect(String userId, String userPassword) {
boolean isValidated = false;
//TODO: Add implementation details
return isValidated;
}
private boolean isUserIdValid(String userId, List<String> userIdList) {
boolean isValidated = false;
//TODO: Add implementation details
return isValidated;
}
public void updateOnlineUserService(String userId){
//TODO updateOnlineUserService for 100 lines of code...
}
public void sendCustomizedLoginMessage(String userId){
//TODO sendCustomizedLoginMessage for 50 lines of code...
}
public void sendOneTimeOffer(String userId){
//TODO sendOneTimeOffer for 100 lines of code...
}}
Now we can see that this class will be huge and complex. It is not a God class by book definition yet, since class fields are commonly used among methods now. But for the sake of argument, we can treat it as a God class and start refactoring.
One of the solutions is to create separate small classes which are used as members in the main class. Another thing you could add, could be separating different behaviors in different interfaces and their respective classes. Hide implementation details in classes by making those methods "private". And use those interfaces in the main class to do its bidding.
So at the end, RefactoredLoginManager will look like this:
public class RefactoredLoginManager {
IDecryptHandler decryptHandler;
IValidateHandler validateHandler;
IOnlineUserServiceNotifier onlineUserServiceNotifier;
IClientDataSender clientDataSender;
public void handleLogin(String hashedUserId, String hashedUserPassword){
String userId = decryptHandler.decryptHashedString(hashedUserId);
String userPassword = decryptHandler.decryptHashedString(hashedUserPassword);
if(!validateHandler.validateUser(userId, userPassword)){ return; }
onlineUserServiceNotifier.updateOnlineUserService(userId);
clientDataSender.sendCustomizedLoginMessage(userId);
clientDataSender.sendOneTimeOffer(userId);
}
}
DecryptHandler:
public class DecryptHandler implements IDecryptHandler {
public String decryptHashedString(String hashedString){
String userId = "";
//TODO Decrypt hashed string for 150 lines of code...
return userId;
}
}
public interface IDecryptHandler {
String decryptHashedString(String hashedString);
}
ValidateHandler:
public class ValidateHandler implements IValidateHandler {
public boolean validateUser(String userId, String userPassword){
//validate for 100 lines of code...
List<String> userIdList = getUserIdList();
if(!isUserIdValid(userId,userIdList)){return false;}
if(!isPasswordCorrect(userId,userPassword)){return false;}
return true;
}
private List<String> getUserIdList() {
List<String> userIdList = new ArrayList<>();
//TODO: Add implementation details
return userIdList;
}
private boolean isPasswordCorrect(String userId, String userPassword)
{
boolean isValidated = false;
//TODO: Add implementation details
return isValidated;
}
private boolean isUserIdValid(String userId, List<String> userIdList)
{
boolean isValidated = false;
//TODO: Add implementation details
return isValidated;
}
}
Important thing to note here is that the interfaces () only has to include the methods used by other classes. So IValidateHandler looks as simple as this:
public interface IValidateHandler {
boolean validateUser(String userId, String userPassword);
}
OnlineUserServiceNotifier:
public class OnlineUserServiceNotifier implements
IOnlineUserServiceNotifier {
public void updateOnlineUserService(String userId){
//TODO updateOnlineUserService for 100 lines of code...
}
}
public interface IOnlineUserServiceNotifier {
void updateOnlineUserService(String userId);
}
ClientDataSender:
public class ClientDataSender implements IClientDataSender {
public void sendCustomizedLoginMessage(String userId){
//TODO sendCustomizedLoginMessage for 50 lines of code...
}
public void sendOneTimeOffer(String userId){
//TODO sendOneTimeOffer for 100 lines of code...
}
}
Since both methods are accessed in LoginHandler, interface has to include both methods:
public interface IClientDataSender {
void sendCustomizedLoginMessage(String userId);
void sendOneTimeOffer(String userId);
}
There are really two topics here:
Given a God class, how its members be rationally partitioned into subsets? The fundamental idea is to group elements by conceptual coherency (often indicated by frequent co-usage in client modules) and by forced dependencies. Obviously the details of this are specific to the system being refactored. The outcome is a desired partition (set of groups) of God class elements.
Given a desired partition, actually making the change. This is difficult if the code base has any scale. Doing this manually, you are almost forced to retain the God class while you modify its accessors to instead call new classes formed from the partitions. And of course you need to test, test, test because it is easy to make a mistake when manually making these changes. When all accesses to the God class are gone, you can finally remove it. This sounds great in theory but it takes a long time in practice if you are facing thousands of compilation units, and you have to get the team members to stop adding accesses to the God interface while you do this. One can, however, apply automated refactoring tools to implement this; with such a tool you specify the partition to the tool and it then modifies the code base in a reliable way. Our DMS can implement this Refactoring C++ God Classes and has been used to make such changes across systems with 3,000 compilation units.
Some I do quite a lot of is read integers from AppSettings. What's the best way to do this?
Rather than do this every time:
int page_size;
if (int.TryParse( ConfigurationManager.AppSettings["PAGE_SIZE"], out page_size){
}
I'm thinking a method in my Helpers class like this:
int GetSettingInt(string key) {
int i;
return int.TryParse(ConfigurationManager.AppSettings[key], out i) ? i : -1;
}
but this is just to save some keystrokes.
Ideally, I'd love to put them all into some kind of structure that I could use intellisense with so I don't end up with run-time errors, but I don't know how I'd approach this... or if this is even possible.
What's a best practices way of getting and reading integers from the AppSettings section of the Web.Config?
ONE MORE THING...
wouldn't it be a good idea to set this as readonly?
readonly int pageSize = Helpers.GetSettingInt("PAGE_SIZE") doesn't seem to work.
I've found an answer to my problem. It involves extra work at first, but in the end, it will reduce errors.
It is found at Scott Allen's blog OdeToCode and here's my implementation:
Create a static class called Config
public static class Config {
public static int PageSize {
get { return int.Parse(ConfigurationManager.AppSettings["PAGE_SIZE"]); }
}
public static int HighlightedProductId {
get {
return int.Parse(ConfigurationManager.AppSettings["HIGHLIGHT_PID"]);
}
}
}
Advantage of doing this are three-fold:
Intellisense
One breakpoint (DRY)
Since I only am writing the Config String ONCE, I do a regular int.Parse.
If someone changes the AppSetting Key, it will break, but I can handle that, as those values aren't changed and the performance is better than a TryParse and it can be fixed in one location.
The solution is so simple... I don't know why I didn't think of it before. Call the values like so:
Config.PageSize
Config.HighlightedProductId
Yay!
I know that this question was asked many years ago, but maybe this answer could be useful for someone. Currently, if you're already receiving an IConfiguration reference in your class constructor, the best way to do it is using GetValue<int>("appsettings-key-goes-here"):
public class MyClass
{
private readonly IConfiguration _configuration;
public MyClass(IConfiguration configuration)
{
_configuration = configuration;
}
public void MyMethod()
{
int value = _configuration.GetValue<int>("appsettings-key-goes-here");
}
}
Take a look at T4Config. I will generate an interface and concrete implementation of your appsettings and connectionstringsections of you web/app config using Lazyloading of the values in the proper data types. It uses a simple T4 template to auto generate things for you.
To avoid creating a bicycle class you could use the following:
System.Configuration.Abstractions.AppSettings.AppSetting<int>("intKey");
https://github.com/davidwhitney/System.Configuration.Abstractions