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Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Archive for July 18th, 2013

Delphi virtual constructors: example of the “Factory” design pattern (via: Stack Overflow)

Posted by jpluimers on 2013/07/18

I bumped into the below answer that I gave a while (what is 4 years in a developer’s life ) on StackOverflow.

It is about Delphi Design Patterns. Sepcifically the Factory Pattern, and explains how virtual constructors implement it.

They are one of the 3 corner stones on which the component based Delphi form designer and object inspector are built:

  • Virtual constructors
  • Properties (events are just a special form of property)
  • Run-Time Type Information.

So here it goes: Read the rest of this entry »

Posted in Delphi, Delphi 1, Delphi 2, Delphi 2005, Delphi 2006, Delphi 2007, Delphi 2009, Delphi 2010, Delphi 3, Delphi 4, Delphi 5, Delphi 6, Delphi 7, Delphi 8, Delphi XE, Delphi XE2, Delphi XE3, Delphi XE4, Development, Software Development | 6 Comments »

C#: combining “adding `char` and `int` and “`a += b` means `a = a + b`, but `a += b + c` does not mean `a = a + b + c`”.

Posted by jpluimers on 2013/07/18

A while ago, I wrote about .NET/C# duh moment of the day: “A char can be implicitly converted to ushort, int, uint, long, ulong, float, double, or decimal (not the other way around; implicit != implicit)”.

There is another duh moment having to do with the various C# operators like += which is being described as being

a += b

is equivalent to

a = a + b

You might think that this also holds:

a += b + c

is equivalent to

a = (a + b) + c

But Eric Lippert has explained this is not the case: it is equivalent to:

a = a + (b + c)

In his explanation, he also shows the confusion can get you very surprising results if you mix string, chars and ints in the expression: depending on the statement and ordering, you either concatenate characters, or add ints to characters.

He also recommends you should not do concatenation: either use String.Format, or StringBuilder. I totally agree with that.

Recommended reading!

–jeroen

Posted in .NET, C#, C# 1.0, C# 2.0, C# 3.0, C# 4.0, C# 5.0, Development, Software Development | Leave a Comment »