Mutable struct

[Kjetil Kristoffer Solberg]

What is a mutable struct?

regards
Kjetil Kristoffer Solberg

[Jon Skeet [C# MVP]]

Kjetil Kristoffer Solberg <kk*@pride.no> wrote:

What is a mutable struct?

One which allows its contents to be changed. Here are two structs, one
immutable and one mutable:

struct Immutable
{
int value;

public Immutable(int value)
{
this.value = value;
}

public int Value
{
get { return value; }
}
}

struct Mutable
{
int value;

public Immutable(int value)
{
this.value = value;
}

public int Value
{
get { return value; }
set { this.value = value; }
}
}

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Kjetil Kristoffer Solberg]

Ok, but in your first example the Immutable structs private int value is set
by the Immutable method. Is it not mutable as well
then? or is a struct mutable only if a value changes through a property?

regards
Kjetil Kristoffer Solberg

"Jon Skeet [C# MVP]" <sk***@pobox.com> wrote in message
news:MP************************@msnews.microsoft.c om...

Kjetil Kristoffer Solberg <kk*@pride.no> wrote:

What is a mutable struct?

One which allows its contents to be changed. Here are two structs, one
immutable and one mutable:

struct Immutable
{
int value;

public Immutable(int value)
{
this.value = value;
}

public int Value
{
get { return value; }
}
}

struct Mutable
{
int value;

public Immutable(int value)
{
this.value = value;
}

public int Value
{
get { return value; }
set { this.value = value; }
}
}

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Paul E Collins]

"Kjetil Kristoffer Solberg" <kk*@pride.no> wrote:

Ok, but in your first example the Immutable structs
private int value is set by the Immutable method.
Is it not mutable as well then? or is a struct mutable
only if a value changes through a property?

The Immutable "method" is the constructor - you can only call it once,
when you create an instance of the struct.

P.

[Dennis Myrén]

The Immutable method is the constructor of the struct.
Meaning that once it has been set, it cannot be changed again.

Immutable immutable = new Immutable(/* value */ 10);
// Now I want to change it but I cant, it throws an Exception.
immutable.Value = 11; // Raises Exception
Mutable mutable= new Mutable(/* value */ 10);
// Now I want to change it AND I can.
mutable.Value = 11; // DO NOT Raise Exception
--
Regards,
Dennis JD Myrén
Oslo Kodebureau
"Kjetil Kristoffer Solberg" <kk*@pride.no> wrote in message
news:%2******************@tk2msftngp13.phx.gbl...

Ok, but in your first example the Immutable structs private int value is set by the Immutable method. Is it not mutable as well
then? or is a struct mutable only if a value changes through a property?

regards
Kjetil Kristoffer Solberg

"Jon Skeet [C# MVP]" <sk***@pobox.com> wrote in message
news:MP************************@msnews.microsoft.c om...

Kjetil Kristoffer Solberg <kk*@pride.no> wrote:

What is a mutable struct?

One which allows its contents to be changed. Here are two structs, one
immutable and one mutable:

struct Immutable
{
int value;

public Immutable(int value)
{
this.value = value;
}

public int Value
{
get { return value; }
}
}

struct Mutable
{
int value;

public Immutable(int value)
{
this.value = value;
}

public int Value
{
get { return value; }
set { this.value = value; }
}
}

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Jon Skeet [C# MVP]]

Dennis Myrén <de****@oslokb.no> wrote:

The Immutable method is the constructor of the struct.
Meaning that once it has been set, it cannot be changed again.
Correct.
Immutable immutable = new Immutable(/* value */ 10);
// Now I want to change it but I cant, it throws an Exception.
immutable.Value = 11; // Raises Exception

No, it doesn't raise an exception - it just doesn't compile in the
first place.

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Jon Skeet [C# MVP]]

Jon Skeet [C# MVP] <sk***@pobox.com> wrote:

struct Mutable
{
int value;

public Immutable(int value)
{
this.value = value;
}

public int Value
{
get { return value; }
set { this.value = value; }
}
}

Apologies - this should, of course, be:

struct Mutable
{
int value;

public Mutable(int value)
{
this.value = value;
}

public int Value
{
get { return value; }
set { this.value = value; }
}
}

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Jon Skeet [C# MVP]]

Dennis Myrén <de****@oslokb.no> wrote:

The Immutable method is the constructor of the struct.
Meaning that once it has been set, it cannot be changed again.
Correct.
Immutable immutable = new Immutable(/* value */ 10);
// Now I want to change it but I cant, it throws an Exception.
immutable.Value = 11; // Raises Exception

No, it doesn't raise an exception - it just doesn't compile in the
first place.

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Dennis Myrén]

Thank you mr Skeet.

--
Regards,
Dennis JD Myrén
Oslo Kodebureau
"Jon Skeet [C# MVP]" <sk***@pobox.com> wrote in message
news:MP***********************@msnews.microsoft.co m...
Dennis Myrén <de****@oslokb.no> wrote:

The Immutable method is the constructor of the struct.
Meaning that once it has been set, it cannot be changed again.
Correct.
Immutable immutable = new Immutable(/* value */ 10);
// Now I want to change it but I cant, it throws an Exception.
immutable.Value = 11; // Raises Exception

No, it doesn't raise an exception - it just doesn't compile in the
first place.

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Jon Skeet [C# MVP]]

Jon Skeet [C# MVP] <sk***@pobox.com> wrote:

struct Mutable
{
int value;

public Immutable(int value)
{
this.value = value;
}

public int Value
{
get { return value; }
set { this.value = value; }
}
}

Apologies - this should, of course, be:

struct Mutable
{
int value;

public Mutable(int value)
{
this.value = value;
}

public int Value
{
get { return value; }
set { this.value = value; }
}
}

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Dennis Myrén]

Thank you mr Skeet.

--
Regards,
Dennis JD Myrén
Oslo Kodebureau
"Jon Skeet [C# MVP]" <sk***@pobox.com> wrote in message
news:MP***********************@msnews.microsoft.co m...
Dennis Myrén <de****@oslokb.no> wrote:

The Immutable method is the constructor of the struct.
Meaning that once it has been set, it cannot be changed again.
Correct.
Immutable immutable = new Immutable(/* value */ 10);
// Now I want to change it but I cant, it throws an Exception.
immutable.Value = 11; // Raises Exception

No, it doesn't raise an exception - it just doesn't compile in the
first place.

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Jay B. Harlow [MVP - Outlook]]

Kjetil,
One thing I like to do is to make the value field in Immutable readonly to
re-emphasize the fact that it is immutable.

Borrowing Jon's example:

struct Immutable
{
readonly int value;

public Immutable(int value)
{
this.value = value;
}

public int Value
{
get { return value; }
}
}
The readonly on value means that it can only be set in the constructor,
every other method you attempt to set it in will receive a compile error.

Hope this helps
Jay

"Kjetil Kristoffer Solberg" <kk*@pride.no> wrote in message
news:%2****************@TK2MSFTNGP15.phx.gbl... What is a mutable struct?

regards
Kjetil Kristoffer Solberg

[Jay B. Harlow [MVP - Outlook]]

Kjetil,
One thing I like to do is to make the value field in Immutable readonly to
re-emphasize the fact that it is immutable.

Borrowing Jon's example:

struct Immutable
{
readonly int value;

public Immutable(int value)
{
this.value = value;
}

public int Value
{
get { return value; }
}
}
The readonly on value means that it can only be set in the constructor,
every other method you attempt to set it in will receive a compile error.

Hope this helps
Jay

"Kjetil Kristoffer Solberg" <kk*@pride.no> wrote in message
news:%2****************@TK2MSFTNGP15.phx.gbl... What is a mutable struct?

regards
Kjetil Kristoffer Solberg