I know the basic differences between a struct and a class, but
apparently not good enough to know why some types/concepts are
implemented as struct whereas most types are implemented as class.
For example, why is DateTime implemented as a struct? Why is BitArray
implemented as a class, but BitVector32 a struct?
In general, in OO design, how do we determine if we should use struct
or class?
12  1562 
>I know the basic differences between a struct and a class, but
apparently not good enough to know why some types/concepts are
implemented as struct whereas most types are implemented as class.
For example, why is DateTime implemented as a struct? Why is BitArray
implemented as a class, but BitVector32 a struct?
In general, in OO design, how do we determine if we should use struct
or class?
I think that, in general, structs are for small things that use a fixed
amount of memory.
On Jul 28, 10:33*am, Author <gnewsgr...@gma il.comwrote:
I know the basic differences between a struct and a class, but
apparently not good enough to know why some types/concepts are
implemented as struct whereas most types are implemented as class.
For example, why is DateTime implemented as a struct? *Why is BitArray
implemented as a class, but BitVector32 a struct?
In general, in OO design, how do we determine if we should use struct
or class?
Struct are placed in memory on the stack, therefore faster and do not
need to be cleaned up with garbage collection. Structs cannot be
extended and cannot extend anything else.
Classes Are on the heap, must be cleaned up and can be extended or
extend.
For most of us, a big "So what?"
I am assuming the choice af struct vs class is something that MS
thinks a lot more about in a framework than the common code grunt and
it comes down to first, performance and then to Symmetry in the code.
thats my take on it.
Tal
Nearly every time I have designed something as a struct I have later
discovered I need to be able to change the values in it and ended up
converting it to a class, so now I just don't bother with them any more.
"Peter Morris" <mr*********@SP AMgmail.comwrot e in message
news:%2******** ********@TK2MSF TNGP06.phx.gbl. ..
Nearly every time I have designed something as a struct I have later
discovered I need to be able to change the values in it and ended up
converting it to a class, so now I just don't bother with them any more.
You can change values in a struct as easily as you can in a class. In fact,
in a lot of ways, you can make a struct act like a class. You can create
properties that you can get and set, just like a class. You can create
methods, you can make field members public. So I'm not really sure what you
mean.
On Jul 28, 12:23*pm, "MC" <for.address.l. ..@www.ai.uga.e du.slash.mc>
wrote:
I know the basic differences between a struct and a class, but
apparently not good enough to know why some types/concepts are
implemented as struct whereas most types are implemented as class.
For example, why is DateTime implemented as a struct? *Why is BitArray
implemented as a class, but BitVector32 a struct?
In general, in OO design, how do we determine if we should use struct
or class?
I think that, in general, structs are for small things that use a fixed
amount of memory.
Hmm, sounds reasonable, at least with regard to BitArray (resizable)
and BitVector32 (not resizable). But is this the only possible reason
that some types are implemented as struct and others class?
I've read the other responses of my question, but they seem to be off-
topic. I would like to hear some guruish comment about my question.
On Mon, 28 Jul 2008 11:53:40 -0700, Fredo <fr***@hotmail. comwrote:
"Peter Morris" <mr*********@SP AMgmail.comwrot e in message
news:%2******** ********@TK2MSF TNGP06.phx.gbl. ..
>Nearly every time I have designed something as a struct I have later
discovered I need to be able to change the values in it and ended up
converting it to a class, so now I just don't bother with them any more.
You can change values in a struct as easily as you can in a class.
Well, yes and no.
There are some serious problems with making a struct mutable. The fact
that structs are _copied_ rather than references leads to code that either
doesn't work as expected (you think you've changed an instance but have
only changed a copy of an instance), or just doesn't compile, or is more
inconvenient than it could or should be.
Pete
On Mon, 28 Jul 2008 11:12:39 -0700, tal_mcmahon <ta*********@ho tmail.com>
wrote:
Struct are placed in memory on the stack,
No. This is a common, but serious misconception.
Structs are "value types". That means that the storage for the type is
allocated where the variable itself is stored. But only local variables
wind up on the stack. A struct used in a class, or in an array, or
anything else that is itself allocated on the heap will wind up on the
heap itself.
therefore faster and do not
need to be cleaned up with garbage collection.
Structs need to be collected when boxed. They also wind up collected
implicitly when they are part of a class that is collected.
In fact, if a struct winds up boxed on a regular basis that will suggest
that the data structure should have been a class after all.
Pete
"Author" <gn********@gma il.comwrote in message
news:00******** *************** ***********@f63 g2000hsf.google groups.com...
On Jul 28, 12:23 pm, "MC" <for.address.l. ..@www.ai.uga.e du.slash.mc>
wrote:
I know the basic differences between a struct and a class, but
apparently not good enough to know why some types/concepts are
implemented as struct whereas most types are implemented as class.
For example, why is DateTime implemented as a struct? Why is BitArray
implemented as a class, but BitVector32 a struct?
In general, in OO design, how do we determine if we should use struct
or class?
I think that, in general, structs are for small things that use a fixed
amount of memory.
Hmm, sounds reasonable, at least with regard to BitArray (resizable)
and BitVector32 (not resizable). But is this the only possible reason
that some types are implemented as struct and others class?
I've read the other responses of my question, but they seem to be off-
topic. I would like to hear some guruish comment about my question.
*************** **************
I'm only a beginner myself, but nobody has mentioned that classes are
inheritable, whereas structs are not. If you are looking at this from an OOP
perspective, this is a huge difference.
To be honest I don't even remember the problems I had, I just remember that
every time I have used them I have ended up switching to classes so now I
don't bother.
Pete
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