In the past when I've done a Constants class, it has looked something like this:
22 public class MyConstants
23 {
24 public const string MyFirstValue = "VALUE1";
25 public const string MySecondValue = "VALUE2";
26 }
Then to use them it goes sort of like this:
17 public class MyClass
18 {
19 public string MyValue { get; set; }
20 }
8 class Program
9 {
10 static void Main(string[] args)
11 {
12 MyClass myObj = new MyClass { MyValue = MyConstants.MyFirstValue };
13 Console.Write(myObj.MyValue);
14 }
15 }
Which would print out "VALUE1".
This works out fine, but has an inherent flaw: you are still just passing around a string, and there is nothing stopping someone from forgetting there is a class of constants and simply assigning their own random string value. This is where JP comes in. In this episode, somewhere near the end, he whips up a quick strongly-typed Constants class, and it works really, really well. Here's what my example above would look like if I had a quarter of Mr. Boodhoo's intelligence:
22 public class MyConstants
23 {
24 public static readonly MyConstants MyFirstValue = new MyConstants();
25 public static readonly MyConstants MySecondValue = new MyConstants();
26
27 private MyConstants() { }
28 }
Now when you use it, it can be typed:
17 public class MyClass
18 {
19 public MyConstants MyValue { get; set; }
20 }
8 class Program
9 {
10 static void Main(string[] args)
11 {
12 MyClass myObj = new MyClass { MyValue = MyConstants.MyFirstValue };
13 Console.Write(myObj.MyValue);
14 }
15 }
Which would print out... ConsoleApplication1.MyConstants? Oh crap, we're only part way there. But JP didn't leave us much to do, we just need to find a way to get a string value out of that object. Here's what our class could look like now:
22 public class MyConstants
23 {
24 public static readonly MyConstants MyFirstValue =
25 new MyConstants("VALUE1");
26 public static readonly MyConstants MySecondValue =
27 new MyConstants("VALUE2");
28 private readonly string value;
29
30 private MyConstants(string value)
31 {
32 this.value = value;
33 }
34
35 public override string ToString()
36 {
37 return value;
38 }
39 }
Now let's use it again:
17 public class MyClass
18 {
19 public MyConstants MyValue { get; set; }
20 }
8 class Program
9 {
10 static void Main(string[] args)
11 {
12 MyClass myObj = new MyClass { MyValue = MyConstants.MyFirstValue };
13 Console.Write(myObj.MyValue.ToString());
14 }
15 }
Pretty sweet eh?
