What is the best way to avoid magic keys? Using string constant keys in a class or using an enumeration?

Question

My idea is to avoid magic string keys in my ASP.NET MVC application. To do this, I want to create string constant keys for sharing in the application.

For example, I can write TempData[MyClass.Message] or TempData[MyEnum.Message.ToString()] instead of TempData["Message"] .

 public class MyClass { public const string Message = "Message"; } 

and

 public enum MyEnum { Message, Others } 

My questions: What is the best way to avoid magic keys? Using string constant keys in a class or using an enum with ToString() ?

Answer 1

It depends on preference and use.

You can take the listed values ​​in a strongly typed way:

 public void SomeFunction(MyEnum someValue) { } 

or

 TempData[MyEnum.Message] 

With constant strings you cannot.

You also have a built-in way of listing the values ​​in an enumeration.

There is a third option that you did not present, and this means that your “constants” are in your configuration settings (App.Config). This will allow you to customize them after compilation. You may not need it now, but you can in the future, so it’s worth considering.

One of them might be better for globalization. I am not sure, since I have never globalized the application. I believe this works in satellite assemblies.

Basically, it comes down to what TempData is, and how you intend to use it.

Answer 2

You should use constant strings as they may contain spaces / special characters if these are your requirements. Otherwise, change TempData to Dictionary<MyEnum,object> , which works best.

Answer 3

I know this was answered, but I want to drop my thoughts here. You are too careful about the mechanics and not the problem you are facing - "how can I avoid breaking my application when I decide that TempData [" Message "] should be a session [" Alert "]" (or that something like that.

Magic strings do not apply to dictionary keys — they apply to messages sent to a routine that do something based on a string value. Something like "SetStatus (" current ")" would be magical.

What you want to do is use a centralized message processing method. Create a helper class for yourself and name it "Messaging", if you want - I get all Railsy and call it "Flash". Then you can do something groovy like “Flash.Message (“ Hello there ”)” - this hides the mechanism (as it should be) and you don’t worry about these dumb dictionary keys.

You can also expand this - "Flash.Alert (" Oh NO! ")" Etc.