Passing null for a class-typed argument renders catchable error ?!?

[seaside]

I have a method

>>>

function appendChildNode( AST $aNewChild ) {
...
}
<<<

where AST is a class. If I pass null, PHP renders this message:

>>>

Catchable fatal error: Argument 1 passed to AST::appendChildNode()
must be an instance of AST, null given, called in /Applications/MAMP/
htdocs/compile/includes/CParser.inc.php(517) : eval()'d code on line 1
and defined in /Applications/MAMP/htdocs/compile/includes/AST.inc.php
on line 43
<<<

Any ideas, why I can't pass a null value?

[appendChildNode() is a method declared inside the class AST]

[Peter Pei]

in php, null is not only a value but also a type, and the type hint was
violated

[seaside]

On 13 Jan., 03:56, "Peter Pei" <[e-mail]:

in php, null is not only a value but also a type, and the type hint was
violated

OK, thx. How do I have to pass a null 'pointer' as an object?

[Rik Wasmus]

On Sun, 13 Jan 2008 03:50:33 +0100, seaside <se********@mac.comwrote:

I have a method

>>>>

function appendChildNode( AST $aNewChild ) {
...
}
<<<

where AST is a class. If I pass null, PHP renders this message:

>>>>

Catchable fatal error: Argument 1 passed to AST::appendChildNode()
must be an instance of AST, null given, called in /Applications/MAMP/
htdocs/compile/includes/CParser.inc.php(517) : eval()'d code on line 1
and defined in /Applications/MAMP/htdocs/compile/includes/AST.inc.php
on line 43
<<<

Any ideas, why I can't pass a null value?

For some reason:

function appendChildNode( AST $aNewChild = NULL ) {
....
}

.... now it will work.
--
Rik Wasmus

[Peter Pei]

buggy. inconsistent lang design

[seaside]

On 13 Jan., 04:00, "Rik Wasmus" <[e-mail]:

On Sun, 13 Jan 2008 03:50:33 +0100, seaside <[e-mail]:

I have a method

* function appendChildNode( AST $aNewChild ) {
* ...
* }
<<<

where AST is a class. If I pass null, PHP renders this message:

Catchable fatal error: Argument 1 passed to AST::appendChildNode()
must be an instance of AST, null given, called in /Applications/MAMP/
htdocs/compile/includes/CParser.inc.php(517) : eval()'d code on line 1
and defined in /Applications/MAMP/htdocs/compile/includes/AST.inc.php
on line 43
<<<

Any ideas, why I can't pass a null value?

For some reason:

function appendChildNode( AST $aNewChild = NULL ) {

}

But now, I can call it 'legally' with no parameters, which I don't
want.
At least any reader would think, 'OK, passing no value is OK'.

Do we have other options?

Additionally: I'll go into details of the code soon, but does the
default value make to
exception disappear, since I passed no value at all to appendChildNode?

[Jerry Stuckle]

seaside wrote:

On 13 Jan., 04:00, "Rik Wasmus" <[e-mail]:

>On Sun, 13 Jan 2008 03:50:33 +0100, seaside <[e-mail]:

>>I have a method
function appendChildNode( AST $aNewChild ) {
...
}
<<<
where AST is a class. If I pass null, PHP renders this message:
Catchable fatal error: Argument 1 passed to AST::appendChildNode()
must be an instance of AST, null given, called in /Applications/MAMP/
htdocs/compile/includes/CParser.inc.php(517) : eval()'d code on line 1
and defined in /Applications/MAMP/htdocs/compile/includes/AST.inc.php
on line 43
<<<
Any ideas, why I can't pass a null value?

For some reason:

function appendChildNode( AST $aNewChild = NULL ) {

}

But now, I can call it 'legally' with no parameters, which I don't
want.
At least any reader would think, 'OK, passing no value is OK'.

Do we have other options?

Additionally: I'll go into details of the code soon, but does the
default value make to
exception disappear, since I passed no value at all to appendChildNode?

As Rik pointed out, type hinting is a somewhat inconsistent operation in
PHP. But this a new area for PHP, and I'm not sure it's been entirely
thought out yet (as seems to be with a lot of things in PHP).

Of course, you could not use type hinting. Instead, you can use
instanceof() in the function itself to ensure you have an instance of
the object. This way you can check for null, also.
--
==================
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
js*******@attglobal.net
==================

[seaside]

On 13 Jan., 04:32, Jerry Stuckle <[e-mail]:

seaside wrote:

On 13 Jan., 04:00, "Rik Wasmus" <[e-mail]:

On Sun, 13 Jan 2008 03:50:33 +0100, seaside <[e-mail]:
I have a method
* function appendChildNode( AST $aNewChild ) {
* ...
* }
<<<
where AST is a class. If I pass null, PHP renders this message:
Catchable fatal error: Argument 1 passed to AST::appendChildNode()
must be an instance of AST, null given, called in /Applications/MAMP/
htdocs/compile/includes/CParser.inc.php(517) : eval()'d code on line 1
and defined in /Applications/MAMP/htdocs/compile/includes/AST.inc.php
on line 43
<<<
Any ideas, why I can't pass a null value?
For some reason:

function appendChildNode( AST $aNewChild = NULL ) {

}

But now, I can call it 'legally' with no parameters, which I don't
want.
At least any reader would think, 'OK, passing no value is OK'.

Do we have other options?

Additionally: I'll go into details of the code soon, but does the
default value make to
exception disappear, since I passed no value at all to appendChildNode?

As Rik pointed out, type hinting is a somewhat inconsistent operation in
PHP. *But this a new area for PHP, and I'm not sure it's been entirely
thought out yet (as seems to be with a lot of things in PHP).

Thx, Jerry! In fact, the app failed to pass a value as an argument to
appendChildNode().

I'm building a parser generator and fetched a returned value from a
non-terminal symbol
from the wrong (let's say) stack frame.

Fixed it, removed the ' = NULL' - and things work fine.

Thx again for all quick answers!

[Michael Fesser]

..oO(seaside)

>On 13 Jan., 04:00, "Rik Wasmus" <[e-mail]:

>For some reason:

function appendChildNode( AST $aNewChild = NULL ) {

}

But now, I can call it 'legally' with no parameters, which I don't
want.

Correct. It's the same as if you explicitly pass NULL.

>At least any reader would think, 'OK, passing no value is OK'.

Do we have other options?

For what? It does exactly what you described in your original posting.

Micha

[Peter Pei]

it is absolutely inconsistent and bad design. null should assume the role of
any type, but not its own type. by saying = null, you are defining a default
value in any other normal cases. here it happens to mean something else.
the slightest inconsistent is inconsistent to me.

[Peter Pei]

You cannot see his concern does not mean there is no concern. the language
is obviously badly defined here. it is forgived, as this is an improving
area in php.

[Michael Fesser]

..oO(Peter Pei)

>it is absolutely inconsistent and bad design.

NACK

>null should assume the role of
any type, but not its own type. by saying = null, you are defining a default
value in any other normal cases. here it happens to mean something else.

It means exactly the same thing - nothing (= no value).

Micha

[Peter Pei]

that's what messed up your brain - nothing and no value. nothing is nothing,
no value is no value.

[Michael Fesser]

..oO(Peter Pei)

>that's what messed up your brain - nothing and no value. nothing is nothing,
no value is no value.

NULL = no value = nothing

Micha