Well, if Java can do it, so can I! Why not make my own C# string class that can do whatever I want it to do? Requirements? Here they are:
- I want it to work just like regular strings
- I want to know if the string is empty just by using it as an if clause, just like Javascript: if (text) doSomething(text);
- I want to see if it's a number just by adding a plus sign in front of it: var number = +text;
- I want to easily know if the string is null or whitespace!
OK, so first I want to get all the functionality of a normal string. So I will just inherit from it! Only I can't.
String is a sealed class in .Net.
Yet there is an abstract class that seems destined to be used by this:
ValueType! It's only implemented by all value types (more or less)
except String, but I will be the next guy to use it! Only I can't. If I try, I get the occult message: "Error CS0644 'EString' cannot derive from special class 'ValueType'". But it does help with something, if I try to inherit from it, it tells me what methods to implement:
Equals, GetHashCode and ToString.
OK, then, I will just do everything from scratch!
Start with a struct (no need for a class) that wraps a string _value field, then overwrite the equality methods:
public struct EString
{
private string _value;
public override bool Equals(object obj)
{
return String.Equals(obj, _value);
}
public override int GetHashCode()
{
return _value == null ? 0 : _value.GetHashCode();
}
public override string ToString()
{
return _value;
}
}
I used 0 for the hash code when the value is null because that's what the .Net object
GetHashCode() does. Now, in order for this to work as a string, I need some
implicit conversion from string to my EString class. So add these two beauties:
public string Value { get => _value; }
private EString(string value) { _value = value; }
public static implicit operator string(EString estring)
{
return estring.Value;
}
public static implicit operator EString(string value)
{
return new EString(value);
}
EString now supports stuff like
EString text="Something";, but I want more! Let's
overload some operators. I want to be able to see if a string is null or empty just like in Javascript:
public static bool operator !(EString estring)
{
return String.IsNullOrEmpty(estring);
}
public static bool operator true(EString estring)
{
return !!estring;
}
public static bool operator false(EString estring)
{
return !estring;
}
Yes, ladies and gentlemen,
true and false are not only boolean constants, but also operators. That doesn't mean something like this is legal:
if (text==true) ..., but you can use stuff like
if (text) ... or
text ? "something" : "empty". Overloading the ! operator allows also something more useful like
if (!text) [this shit is empty].
Moar! How about a simple way to know if the string is null or empty or whitespace? Let's overload the ~ operator. How about getting the number encoded into the text? Let's overload the + operator. Here is the final result:
public struct EString
{
private string _value;
public string Value { get => _value; }
private EString(string value) { _value = value; }
public override bool Equals(object obj)
{
return String.Equals(obj, _value);
}
public override int GetHashCode()
{
return _value == null ? 0 : _value.GetHashCode();
}
public override string ToString()
{
return _value;
}
public static bool operator !(EString estring)
{
return String.IsNullOrEmpty(estring);
}
public static bool operator true(EString estring)
{
return !!estring;
}
public static bool operator false(EString estring)
{
return !estring;
}
public static bool operator ~(EString estring)
{
return String.IsNullOrWhiteSpace(estring);
}
public static decimal operator +(EString estring)
{
return decimal.TryParse(estring.Value, out decimal d) ? d : decimal.Zero;
}
public static implicit operator string(EString estring)
{
return estring.Value;
}
public static implicit operator EString(string value)
{
return new EString(value);
}
}
Disclamer: I did this mostly for fun. I can't condone replacing your strings with my class, but look at these examples for usage:
EString s=inputText;
if (!~s) {
var d = Math.Round(+s,2);
if (d != 0) {
Console.WriteLine("Number was introduced: "+d);
}
}
You might wonder what a fractional number in a book series means. For some authors, it means books that are part of the universe, but not of the story, inbetween events that are defined maybe just chronologically. For others, it's even less, short stories that bring completion to their vision, different in scope, style and/or characters from the main books that maybe made you find and read them.
