get an object property

if i have an expression that evaluates to an object, the return value from a
function, say, and i only want the value of one of the objects properties,
is there a tidy way to get it without setting another variable?

to illustrate, here's something that doesn't work, but it would be
convenient if it did:

$o = array( (object) array('a'=>1), (object) array('a'=>2) );

if ( end($o)->a > 1 ) { // can't use -> like this!
....
}




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Re: get an object property

Wouldn't it be $o[1]->a?

J Corry
Sent from my iPhone

On Sep 11, 2009, at 7:31 PM, Tom Worster wrote:

> if i have an expression that evaluates to an object, the return
> value from a
> function, say, and i only want the value of one of the objects
> properties,
> is there a tidy way to get it without setting another variable?
>
> to illustrate, here's something that doesn't work, but it would be
> convenient if it did:
>
> $o = array( (object) array('a'=>1), (object) array('a'=>2) );
>
> if ( end($o)->a > 1 ) { // can't use -> like this!
> ...
> }
>
>
>
>
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> To unsubscribe, visit: http://www.php.net/unsub.php
>

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Re: get an object property

On Fri, Sep 11, 2009 at 07:31:01PM -0400, Tom Worster wrote:

> if i have an expression that evaluates to an object, the return value from a
> function, say, and i only want the value of one of the objects properties,
> is there a tidy way to get it without setting another variable?
>
> to illustrate, here's something that doesn't work, but it would be
> convenient if it did:
>
> $o = array( (object) array('a'=>1), (object) array('a'=>2) );
>
> if ( end($o)->a > 1 ) { // can't use -> like this!
> ...
> }
>

You should use print_r() or var_dump() to investigate what happens when
you try to cast an array into an object. I myself don't know what would
happen. Also, what's allowed and what effects are produced could depend
heavily on the version of PHP you're running. Version 4 != 5 != 5.3 in
this respect.

Paul

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Re: get an object property

Tom Worster wrote:
> if i have an expression that evaluates to an object, the return value from a
> function, say, and i only want the value of one of the objects properties,
> is there a tidy way to get it without setting another variable?
>
> to illustrate, here's something that doesn't work, but it would be
> convenient if it did:
>
> $o = array( (object) array('a'=>1), (object) array('a'=>2) );
>
> if ( end($o)->a > 1 ) { // can't use -> like this!
> ...
> }

What version of PHP are you using? Your example should work.


Torben

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Re: get an object property

On 9/12/09 12:31 AM, "Paul M Foster" wrote:

> On Fri, Sep 11, 2009 at 07:31:01PM -0400, Tom Worster wrote:
>
>> if i have an expression that evaluates to an object, the return value from a
>> function, say, and i only want the value of one of the objects properties,
>> is there a tidy way to get it without setting another variable?
>>
>> to illustrate, here's something that doesn't work, but it would be
>> convenient if it did:
>>
>> $o = array( (object) array('a'=>1), (object) array('a'=>2) );
>>
>> if ( end($o)->a > 1 ) { // can't use -> like this!
>> ...
>> }
>>
>
> You should use print_r() or var_dump() to investigate what happens when
> you try to cast an array into an object. I myself don't know what would
> happen. Also, what's allowed and what effects are produced could depend
> heavily on the version of PHP you're running. Version 4 != 5 != 5.3 in
> this respect.

i did that long ago when i was looking for php's object literal syntax. i
didn't find one. we discussed it here more recently and consensus appeared
to be that casting an array was the most convenient workaround.



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Re: get an object property

On 9/12/09 1:32 AM, "Lars Torben Wilson" wrote:

> Tom Worster wrote:
>> if i have an expression that evaluates to an object, the return value from a
>> function, say, and i only want the value of one of the objects properties,
>> is there a tidy way to get it without setting another variable?
>>
>> to illustrate, here's something that doesn't work, but it would be
>> convenient if it did:
>>
>> $o = array( (object) array('a'=>1), (object) array('a'=>2) );
>>
>> if ( end($o)->a > 1 ) { // can't use -> like this!
>> ...
>> }
>
> What version of PHP are you using? Your example should work.
>
> Torben

5.2.9.

what version does it work in?



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Re: get an object property

On 9/12/09 9:50 AM, "Tom Worster" wrote:

> On 9/12/09 1:32 AM, "Lars Torben Wilson" wrote:
>
>> Tom Worster wrote:
>>> if i have an expression that evaluates to an object, the return value from a
>>> function, say, and i only want the value of one of the objects properties,
>>> is there a tidy way to get it without setting another variable?
>>>
>>> to illustrate, here's something that doesn't work, but it would be
>>> convenient if it did:
>>>
>>> $o = array( (object) array('a'=>1), (object) array('a'=>2) );
>>>
>>> if ( end($o)->a > 1 ) { // can't use -> like this!
>>> ...
>>> }
>>
>> What version of PHP are you using? Your example should work.
>>
>> Torben
>
> 5.2.9.
>
> what version does it work in?

i shamefully beg your pardon, lars. i was sure i tested the example but it's
clear to me now i either didn't or i made a mistake. end($o)->a IS php
syntax! so -> may follow a function (or method, i guess) call.

but let me give you a more different example:

$a and $b are normally both objects, each with various members including a
prop q, but sometimes $a is false. i want the q of $a if $a isn't false,
otherwise that of $b.

($a ? $a : $b)->q // is not php, afaik

before you suggest one, i know there are simple workarounds.

but mine is a theoretical question about syntax, not a practical one. i'm
exploring php's syntactic constraints on the -> operator in contrast to,
say, the + or . operators. and in contrast to other languages.

for example, the . in js seems more generally allowed than -> (or, for that
matter, []) in php. programmers (especially using jquery) are familiar with
using . after an expression that evaluates to an object, e.g.

My x class number is

Re: get an object property

> echo a()['q']; // isn't?

because this is simply not valid syntax for the INTERPRETER PHP

while this
> echo o()->q;
can be interpreted because of the design of the interpreter.

I can live with that.

ralph_deffke@yahoo.de

"Tom Worster" wrote in message
news:C6D13522.12422%fsb@thefsb.org...
> On 9/12/09 9:50 AM, "Tom Worster" wrote:
>
> > On 9/12/09 1:32 AM, "Lars Torben Wilson" wrote:
> >
> >> Tom Worster wrote:
> >>> if i have an expression that evaluates to an object, the return value
from a
> >>> function, say, and i only want the value of one of the objects
properties,
> >>> is there a tidy way to get it without setting another variable?
> >>>
> >>> to illustrate, here's something that doesn't work, but it would be
> >>> convenient if it did:
> >>>
> >>> $o = array( (object) array('a'=>1), (object) array('a'=>2) );
> >>>
> >>> if ( end($o)->a > 1 ) { // can't use -> like this!
> >>> ...
> >>> }
> >>
> >> What version of PHP are you using? Your example should work.
> >>
> >> Torben
> >
> > 5.2.9.
> >
> > what version does it work in?
>
> i shamefully beg your pardon, lars. i was sure i tested the example but
it's
> clear to me now i either didn't or i made a mistake. end($o)->a IS php
> syntax! so -> may follow a function (or method, i guess) call.
>
> but let me give you a more different example:
>
> $a and $b are normally both objects, each with various members including a
> prop q, but sometimes $a is false. i want the q of $a if $a isn't false,
> otherwise that of $b.
>
> ($a ? $a : $b)->q // is not php, afaik
>
> before you suggest one, i know there are simple workarounds.
>
> but mine is a theoretical question about syntax, not a practical one. i'm
> exploring php's syntactic constraints on the -> operator in contrast to,
> say, the + or . operators. and in contrast to other languages.
>
> for example, the . in js seems more generally allowed than -> (or, for
that
> matter, []) in php. programmers (especially using jquery) are familiar
with
> using . after an expression that evaluates to an object, e.g.
>
>
>

My x class number is
>

RE: get an object property

I have to agree, your example works fine for me. For testing I used the
latest stable Release of server2go with PHP 5.2.10.

Or do you want to use something like that:

class o
{
protected $arr =3D array('a'=3D>0);
function o($n){$this->arr['a'] =3D $n;}
function getA(){return $this->arr['a'];}
}

$o =3D array( new o(1), new o(2) );


if ( end($o)->getA() > 1 ) { =20
echo "yeah";
}

Which works fine as well ...=20

Regards,
jan

-----Original Message-----
From: Tom Worster [mailto:fsb@thefsb.org]=20
Sent: Saturday, September 12, 2009 1:31 AM
To: PHP General List
Subject: [PHP] get an object property

if i have an expression that evaluates to an object, the return value =
from a
function, say, and i only want the value of one of the objects =
properties,
is there a tidy way to get it without setting another variable?

to illustrate, here's something that doesn't work, but it would be
convenient if it did:

$o =3D array( (object) array('a'=3D>1), (object) array('a'=3D>2) );

if ( end($o)->a > 1 ) { // can't use -> like this!
....
}




--=20
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Eingehende eMail ist virenfrei.
Von AVG überprüft - www.avg.de=20
Version: 8.5.409 / Virendatenbank: 270.13.71/2336 - Ausgabedatum: =
09/11/09
09:15:00=20


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Re: get an object property

Tom Worster wrote:
> On 9/12/09 9:50 AM, "Tom Worster" wrote:
>
>
>> On 9/12/09 1:32 AM, "Lars Torben Wilson" wrote:
>>
>>
>>> Tom Worster wrote:
>>>
>>>> if i have an expression that evaluates to an object, the return value from a
>>>> function, say, and i only want the value of one of the objects properties,
>>>> is there a tidy way to get it without setting another variable?
>>>>
>>>> to illustrate, here's something that doesn't work, but it would be
>>>> convenient if it did:
>>>>
>>>> $o = array( (object) array('a'=>1), (object) array('a'=>2) );
>>>>
>>>> if ( end($o)->a > 1 ) { // can't use -> like this!
>>>> ...
>>>> }
>>>>
>>> What version of PHP are you using? Your example should work.
>>>
>>> Torben
>>>
>> 5.2.9.
>>
>> what version does it work in?
>>
>
> i shamefully beg your pardon, lars. i was sure i tested the example but it's
> clear to me now i either didn't or i made a mistake. end($o)->a IS php
> syntax! so -> may follow a function (or method, i guess) call.
>
No need for apologies. :)
> but let me give you a more different example:
>
> $a and $b are normally both objects, each with various members including a
> prop q, but sometimes $a is false. i want the q of $a if $a isn't false,
> otherwise that of $b.
>
> ($a ? $a : $b)->q // is not php, afaik
>
> before you suggest one, i know there are simple workarounds.
>
You're right, that isn't PHP syntax. One workaround that came to mind
which does
a similar thing (although using a different mechanism) is this:

${$a ? 'a' : 'b'}->q

> but mine is a theoretical question about syntax, not a practical one. i'm
> exploring php's syntactic constraints on the -> operator in contrast to,
> say, the + or . operators. and in contrast to other languages.
>
I can respect that. This kind of exploration is often quite illuminating.
> for example, the . in js seems more generally allowed than -> (or, for that
> matter, []) in php. programmers (especially using jquery) are familiar with
> using . after an expression that evaluates to an object, e.g.
>
>
>

My x class number is
>

Re: get an object property

On 9/13/09 3:21 AM, "Lars Torben Wilson" wrote:

>> On 9/12/09 9:50 AM, "Tom Worster" wrote:
>>
>> but let me give you a more different example:
>>
>> $a and $b are normally both objects, each with various members including a
>> prop q, but sometimes $a is false. i want the q of $a if $a isn't false,
>> otherwise that of $b.
>>
>> ($a ? $a : $b)->q // is not php, afaik
>>
>> before you suggest one, i know there are simple workarounds.
>>
> You're right, that isn't PHP syntax. One workaround that came to mind
> which does
> a similar thing (although using a different mechanism) is this:
>
> ${$a ? 'a' : 'b'}->q

i would not have thought of that. interesting...


>> and while i'm at it, and using my original error, how come...
>>
>> function o() { return (object) array('q'=>7); }
>> echo o()->q; // is ok syntax, but
>>
>> function a() { return array('q'=>5); }
>> echo a()['q']; // isn't?
>>
> I'm afraid I can't answer that right now--it does perhaps seem
> inconsistent at first glance,
> although I can't say I've ever missed it or felt that using syntax like
> that would make my
> life any better. Maybe it would. Then again, I can also see an argument
> being made for
> allowing the object syntax but not the array syntax: in the case of
> objects, you can have
> a clean class declaration which is pretty much self-documenting, and
> later users of the
> class can have a clear idea of which properties are available and which
> are not, and they
> can thus be sure that o()->q will not result in uninitialized property
> problems. Using the
> array syntax you could never be sure that the index requested actually
> exists.
>
> Of course, this holds true only for people like me who don't really like
> the idea of creating
> objects on the fly in PHP unless there's a very good reason to. Usually
> in PHP such tasks
> are better handled by arrays anyway.

the dbms abstraction library i use delivers rows, by default, as objects. so
i commonly handle dynamically generated data in the form of objects, though
it's not my code generating those objects. i think that's one reasons why i
often find i would use objects as data structures. and because i find the
dynamic objects in js convenient.

but i think you're preference reflects more closely was probably the concept
of php's version of oop: an object is an instances of a static class.

in any case, now that i've confirmed that i'm not merely unaware of the
features i was hunting for, and that they don't exist by design, i can
perhaps move on.

on a related note, way back when xml was ascendant as "the most exciting new
technology to hit the net since java", i was not impressed. what a horrid
syntax for specifying and communicating data, i would argue. why not use the
syntax from some sensible programming language instead? js, for example?
easy to parse, less overhead, human readable (i find xml hard to read), etc.
then eventually json happened, without all the hype and fanfare, just doing
the job very conveniently. i love it.

and to make that comment vaguely php related, i now use json to encode
structured data that i want to write to the php error log.



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Re: get an object property

Tom Worster wrote:
> On 9/13/09 3:21 AM, "Lars Torben Wilson" wrote:
>
>
>>> On 9/12/09 9:50 AM, "Tom Worster" wrote:
>>>
>>> but let me give you a more different example:
>>>
>>> $a and $b are normally both objects, each with various members including a
>>> prop q, but sometimes $a is false. i want the q of $a if $a isn't false,
>>> otherwise that of $b.
>>>
>>> ($a ? $a : $b)->q // is not php, afaik
>>>
>>> before you suggest one, i know there are simple workarounds.
>>>
>>>
>> You're right, that isn't PHP syntax. One workaround that came to mind
>> which does
>> a similar thing (although using a different mechanism) is this:
>>
>> ${$a ? 'a' : 'b'}->q
>>
>
> i would not have thought of that. interesting...
>
>
>
>>> and while i'm at it, and using my original error, how come...
>>>
>>> function o() { return (object) array('q'=>7); }
>>> echo o()->q; // is ok syntax, but
>>>
>>> function a() { return array('q'=>5); }
>>> echo a()['q']; // isn't?
>>>
>>>
>> I'm afraid I can't answer that right now--it does perhaps seem
>> inconsistent at first glance,
>> although I can't say I've ever missed it or felt that using syntax like
>> that would make my
>> life any better. Maybe it would. Then again, I can also see an argument
>> being made for
>> allowing the object syntax but not the array syntax: in the case of
>> objects, you can have
>> a clean class declaration which is pretty much self-documenting, and
>> later users of the
>> class can have a clear idea of which properties are available and which
>> are not, and they
>> can thus be sure that o()->q will not result in uninitialized property
>> problems. Using the
>> array syntax you could never be sure that the index requested actually
>> exists.
>>
>> Of course, this holds true only for people like me who don't really like
>> the idea of creating
>> objects on the fly in PHP unless there's a very good reason to. Usually
>> in PHP such tasks
>> are better handled by arrays anyway.
>>
>
> the dbms abstraction library i use delivers rows, by default, as objects. so
> i commonly handle dynamically generated data in the form of objects, though
> it's not my code generating those objects. i think that's one reasons why i
> often find i would use objects as data structures. and because i find the
> dynamic objects in js convenient.
>
>
Yeah. . .never been a fan of the libs which return objects, although
such a model does
perhaps have its uses.
> but i think you're preference reflects more closely was probably the concept
> of php's version of oop: an object is an instances of a static class.
>
>

Yes, I'd say the same thing, except I'd replace the term 'static' with
'declared'. If an
object is created on the fly, in someone else's code, and I have to
maintain that code,
then either that code must be well-documented or I have to go on a hunt
through
the source code to find out what might be available within that object.
Not my idea
of fun. Convenient for the original coder, perhaps, especially if they
come from an
automatic model background such as Javascript. And maybe one day I'll
come to
love it. So far I haven't seen enough of a benefit to convince me that
it's worth the
long-term maintenance headache it can (note that I say "can", not
"does") cause.

> in any case, now that i've confirmed that i'm not merely unaware of the
> features i was hunting for, and that they don't exist by design, i can
> perhaps move on.
>
> on a related note, way back when xml was ascendant as "the most exciting new
> technology to hit the net since java", i was not impressed. what a horrid
> syntax for specifying and communicating data, i would argue. why not use the
> syntax from some sensible programming language instead? js, for example?
> easy to parse, less overhead, human readable (i find xml hard to read), etc.
> then eventually json happened, without all the hype and fanfare, just doing
> the job very conveniently. i love it.
>
>
I also never found myself sold on the "XML everywhere" philosophy which
seemed to
spring up during its first few years. I have found it useful for certain
things--usually
involving documents. :) It's awesome for technical documentation such as
working on
the PHP manual; I've used it when writing books; and XML and the DOM can
be a
great help when constructing automatically validated XHTML. But there
are also many
other things which people insisted it would be perfect for which just
end up being a
waste of cycles and memory. It's a good tool for some tasks but
completely ill-suited
for others IMHO.

I like the idea of json when working with Javascript. Years ago (before
var_export())
I wrote something very similar to var_export() which would write out a
human-readable
and directly PHP-parseable string for structured data. Sort of like. .
..er. . .pson (*cough*). ;)
> and to make that comment vaguely php related, i now use json to encode
> structured data that i want to write to the php error log.
>
Interesting. For something like that I would just use var_export() and
skip the overhead
of parsing json back into PHP if I needed to do that. I'd use json when
using Javascript, though.
But whatever makes you happy--I'm certainly not here to try to change
anybody's mind
about that sort of thing.

Cheers, and good luck with the explorations!


Regards,

Torben

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