Question regarding anonymous methods as class members

Question

I am developing a PHP mini-framework, one of whose methods builds an HTML table from an array of objects:

class HTMLTableField {
    private $hdr;
    private $alg;
    private $fun;

    function __construct($descr, $align, $apply) {
        # fun must be an anonymous function
        $this->hdr = '<th>' . htmlentities($descr) . "</th>\n";     
        $this->alg = "<td style=\"text-align: {$align}\">";
        $this->fun = $apply;
    }

    function getHeader() {
        return $this->hdr;
    }

    function getCell($row) {
        # This line fails
        return "{$this->alg}{$this->fun($row)}</td>";
    }
}

function gen_html_table($rows, $fields) {
    # $fields must be an array of HTMLTableField objects
    echo "<table>\n<thead>\n<tr>\n";
    foreach ($fields as $field)
        echo $field->getHeader();
    echo "</tr>\n</thead>\n<tbody>\n";
    foreach ($rows as $row) {
        echo "<tr>\n";
        foreach ($fields as $field)
            echo $field->getCell($row);
        echo "</tr>\n";
    }
    echo "</tbody>\n</table>\n";
}

However, when the flow of control of gen_html_table reaches

echo $field->getCell($row);

I get an error: "Call to undefined method HTMLTableField::fun()." But fun is supposed to be an anonymous method!

score 2 · Answer 1 · edited Dec 06 '11 at 13:59

2

There is even shorter and in my opinion more elegant solution:

function getCell($row) {
    return "{$this->alg}{$this->fun->__invoke($row)}</td>";
}

edited Dec 06 '11 at 13:59

edorian

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answered Dec 06 '11 at 12:32

Lukáš Krejčí

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score 1 · Answer 2 · answered Jan 14 '11 at 00:13

1

Never mind. I found an ugly, but ultimately working solution:

$func = $this->fun;
return "{$this->alg}{$func($row)}</td>";

answered Jan 14 '11 at 00:13

isekaijin

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score 1 · Answer 3 · answered Jan 14 '11 at 00:18

1

I'm not sure what you are try to accomplish but are you not better off using Magic Methods http://www.php.net/manual/en/language.oop5.overloading.php#language.oop5.overloading.methods?

answered Jan 14 '11 at 00:18

Matt Lowden

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No, this time magic methods won't help. `fun` is an *anonymous* function. – isekaijin Jan 14 '11 at 00:22

score 1 · Answer 4 · answered Jan 14 '11 at 00:19

1

One way to do this is:

call_user_func($this->fun, $row)

I suppose it's a matter of style, but a lot of time using call_user_func() or call_user_func_array() is considered cleaner than $func() syntax, and in some cases (such as this one), necessary. It also makes it easier to spot dynamic calls right away.

answered Jan 14 '11 at 00:19

mfonda

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Yeah, but I wish `$($this->fun)($row)` were possible. – isekaijin Jan 14 '11 at 00:21
@Eduardo `call_user_func[_array]` is the PHP way. – mfonda Jan 14 '11 at 00:23
I'm a C++ programmer who happens to be using PHP out of necessity. A FORTRAN programmer can write FORTRAN programs in any language. A C++ programmer hates all other languages, because he cannot write C++ programs in them. – isekaijin Jan 14 '11 at 00:25

score 1 · Accepted Answer · answered Jan 14 '11 at 00:22

1

you can't use an anynomious function via the class property.

function getCell($row) {
    # This line works
    $fun = $this->fun;
    return $this->alg . $fun($row) . "</td>";
}

makes your script running :), tested on php 5.3.1

answered Jan 14 '11 at 00:22

Samuel Herzog

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Yup, it's what I just did. But it's not very elegant. – isekaijin Jan 14 '11 at 00:23
i like to read it more than `call_user_func()`. sadly there is no better way. – Samuel Herzog Jan 14 '11 at 00:34
Yeah, `call_user_func()` makes it feel as if reflection weren't native to PHP, but rather hacked into it. – isekaijin Jan 14 '11 at 00:38

score 0 · Answer 6 · answered Jan 14 '11 at 00:04

0

I think you need

$this->$fun($row)

rather than

$this->fun($row)

The former calls the function pointer stored in the member variable $fun, while the latter calls the member function fun(), which as pointed out does not exist.

answered Jan 14 '11 at 00:04

JSBձոգչ

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Oh. I thought `$fun` was used to use a **string** as the name of a function. – isekaijin Jan 14 '11 at 00:06
@Eduardo, it can do that, too, but that's definitely not recommended! – JSBձոգչ Jan 14 '11 at 00:08
The left-brained C++ programmer in me wants to use `$($this->fun)`. – isekaijin Jan 14 '11 at 00:09
Actually, I kind of suspect your problem is the fact that you're inside a quote, which complicates string parsing. Have you tried teasing out the anonymous function call onto its own line? – JSBձոգչ Jan 14 '11 at 00:14
Nope. But I tried extracting the anonymous function into a temporary variable, which worked like a charm. – isekaijin Jan 14 '11 at 00:17
@Eduardo, your solution is exactly what I was trying to suggest with my previous comment :). – JSBձոգչ Jan 14 '11 at 00:20

Question regarding anonymous methods as class members

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