PHP array with default value for nonexisting indices - php

Question

I love the Hash implementation of Ruby where you can initialize the Hash object with a default value. At the moment I'm struggling with implementing a similar object in PHP. This is my first (non-working) shot at this.
class DefaultArray extends ArrayObject {
protected $_defaultValue;
public function setDefault($defaultValue) {
$this->_defaultValue = $defaultValue;
}
public function offsetExists($index) {
return true;
}
public function offsetGet($index) {
if(!parent::offsetExists($index)) {
if(is_object($this->_defaultValue))
$default = clone $this->_defaultValue;
else
$default = $this->_defaultValue;
parent::offsetSet($index, $default);
}
return parent::offsetGet($index);
}
}
$da = new DefaultArray();
assert($da["dummy"] == null);
$da->setDefault = 1;
assert($da["dummy2"] == 1);
The second assertion will fail. Stepping through the code shows that offsetGet is called and the if clause is executed. Nevertheless any array value is null. Any ideas for alternative implementations?
I'm tired of writing
if(!isset($myarr['value']))
$myarr['value'] = new MyObj();
$myarr['value']->myVal=5;
instead of just writing
$myarr['value']->myVal=5;

Answer 1

$da->setDefault(1);
You can also use the __construct magic function:
class DefaultArray extends ArrayObject
{
public function __construct($value = null){
if(is_null($value))
{
$this->value = 'default';
} else {
$this->value = $value;
}
}
}

Answer 2

Try the magic methods __get.
class DefaultArray extends ArrayObject {
protected $_defaultValue;
public function setDefault($defaultValue) {
$this->_defaultValue = $defaultValue;
}
public function __get($index) {
return $this->offsetGet($index);
}
public function offsetGet($index) {
if(!parent::offsetExists($index)) {
if (is_object($this->_defaultValue)) {
$default = clone $this->_defaultValue;
} else {
$default = $this->_defaultValue;
}
parent::offsetSet($index, $default);
}
return parent::offsetGet($index);
}
}
Now you just need to use different keys as the read access will initialize that array items:
$da = new DefaultArray();
assert($da['foo'] == null);
$da->setDefault(1);
assert($da['bar'] == 1);

Answer 3

You could use my tiny library ValueResolver in this case, for example:
class DefaultArray extends ArrayObject
{
public function __construct($value = null){
$this->value = ValueResolver::resolve($value, 'default'); // returns 'default' if $value is null
}
}
and don't forget to use namespace use LapaLabs\ValueResolver\Resolver\ValueResolver;
There are also ability to typecasting, for example if your variable's value should be integer, so use this:
$id = ValueResolver::toInteger('6 apples', 1); // returns 6
$id = ValueResolver::toInteger('There are no apples', 1); // returns 1 (used default value)
Check the docs for more examples

Answer 4

Why so complicated?
function initVal($value) {
global $myarr;
if(!isset($myarr['value']))
$myarr['value'] = new MyObj();
}
Now you just have to call:
initVal('bla');
$myarr['bla']->bla = 'bla';
But I see, yours is much more neat.