Implementing IComparable<> in a sealed struct for comparison in a generic function
I have a C# .net 2.0 CF application where I'm validating the return value from an object. I cannot modify this structure or t开发者_如何学Pythonhe function that returns it.
/// This structure is returned by a function from the object under test
public struct SomeType
{
int a;
int b;
char c;
string d;
public static SomeType Empty { get { return new SomeType(); } }
}
/// pretend this function is in the object under test
static SomeType FunctionUnderTest()
{
return SomeType.Empty;
}
Since I may have to do this for many functions returning many different types, I wanted to use a generic comparison function. This is open to modification.
static bool Compare<T>(ValidationTypes ValidateCond,
T ActualValue,
T ExpectedValue) where T : System.IComparable<T>
{
switch (ValidateCond)
{
case ValidationTypes.Equal:
return ActualValue.CompareTo(ExpectedValue) == 0;
case ValidationTypes.NotEqual:
return ActualValue.CompareTo(ExpectedValue) != 0;
case ValidationTypes.LessThan:
return ActualValue.CompareTo(ExpectedValue) < 0;
// more interesting things...
}
return false;
}
But, that means the structure returned from the function under test has to implement the System.IComparable<> interface. I was thinking something like this, which obviously won't work since structs are sealed, but should give you an idea of what I'm looking for:
/// our test creates a custom version of this structure that derives from
/// the System.IComparable<> interface.
public class SomeTypeUnderTest : SomeType, System.IComparable<SomeTypeUnderTest>
{
#region IComparable<SomeTypeUnderTest> Members
public int CompareTo(SomeTypeUnderTest other)
{
// insert some comparison function between object and this
return 0;
}
#endregion
}
Thus, I could use it like this:
bool res = Type<int>(ValidationTypes.Equal, 1, 2);
bool res2 = Type<SomeTypeUnderTest>(ValidationTypes.Equal,
new FunctionUnderTest(),
new SomeType.Empty);
Please, let me know if anybody has any suggestions on how to properly do this.
Have you thought about implementing the IComparer<T> interface for your structure?
The type wouldn't implement comparisons itself. When you want to compare two values, you would use the IComparer<T> instance instead.
int result1 = Comparer<int>.Default.Compare(1, 2);
// the Default comparer defaults
// to IComparable<T>.CompareTo
int result2 = new SomeTypeComparer().Compare(FuncUnderTest(), SomeType.Empty);
I would propose to introduce a new parameter to static bool Compare(), which is of type Comparison (delegate int Comparison(T a, T b)) or IComparer, can call it rather than value.CompareTo
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