PHP Method Chaining setting and getting a value - php

Question

I'm currently studying OOP Method Chaining, but I'm having difficulties from making it work.
I've created setValue method where it returns a value based on the parameters.
Then, I've created setLabel method and added a parameter to be used after a setValue has been called.
Here is the current code I have:-
class Field
{
public $label;
public function setValue($property, $value)
{
$this->$property = new \stdClass();
$this->$property->value = $value;
$this->$property->label = $this->label;
return $this;
}
public function setLabel($label)
{
return $this->label = $label;
}
}
A sample code for retrieving the data:-
$field = new Field;
$field->setValue('textfield', 'something to print')->setLabel('Label here');
print $field->textfield->value; // Returns the value
print $field->textfield->label; // Returns an empty string
I can't figure out what's wrong with my code. Please help.

Answer 1

Assuming that the following is your goal:
print $field->textfield->value; // Returns the value
print $field->textfield->label; // Returns the label
if you want this to work:
$field = new Field;
$field->setValue('textfield', 'something to print')->setLabel('Label here');
Then you need to do something like this:
class FieldProperty {
public $label
public $value;
public setValue($value) { $this->value = $value; return $this; }
public setLabel($label) { $this->label = $label; return $this; }
}
class Field
{
public function setValue($property, $value)
{
$this->$property = new FieldProperty();
$this->$property->setValue($value);
return $this->$property;
}
}
Thinking about it further, we can add:
class Field
{
public function setValue($property, $value)
{
$this->$property = new FieldProperty();
$this->$property->setValue($value);
return $this->$property;
}
public function setProperty($propertyName)
{
$this->$propertyName = new FieldProperty;
return $this->$propertyName;
}
}
Now you can do this:
$field->setProperty('textfield')->setLabel('my label')->setValue('some value');

Answer 2

If you want to maintain a reference between $this->$property->label and $this->label, assign the value by reference
$this->$property->label =& $this->label;
Demo ~ https://eval.in/955943
Be warned, the reference works both ways so if you assign a new label to $field->textfield->label, it will also change $field->label.
I feel a better approach would be to use magic methods to automatically create each property. Then you can keep track of them all in a private field and update their labels accordingly.
class Field
{
public $label;
private $properties = []; // this will store all your dynamic properties
public function __get($name) {
// lazily create properties on demand
if (!isset($this->properties[$name])) {
$this->properties[$name] = new \stdclass();
}
return $this->properties[$name];
}
public function setValue($property, $value)
{
// this will automatically create "$property" if it's not defined
$this->$property->value = $value;
$this->$property->label = $this->label;
return $this;
}
public function setLabel($label)
{
// Set the field label and any known property labels
$this->label = $label;
foreach($this->properties as $property) {
$property->label = $label;
}
return $label; // ¯\_(ツ)_/¯
}
}

Answer 3

If you want to do it OOP way, I guess, I need to do it like the following. Create the base Field class:
class Field
{
public $value;
public $label;
public function setValue($value)
{
$this->value = $value;
return $this;
}
public function setLabel($label)
{
$this->label = $label;
return $this;
}
}
Maybe, even make it abstract.
Then you can extend this class, creating specific fields:
final class TextField extends Field
{
}
$textField = (new TextField)
->setValue('something to print')
->setLabel('Label here');
Here is the demo.
This way, you can utilize polymorphism later in your program. Say you have an object, to which you pass a bunch of different objects of type Field (read extend Field). Then doing your way, this object wouldn't know what $property each of them has, and it wouldn't be able to access value and label - the objects don't share the common interface. But, with objects, that share the common interface (in our case extend the same base class), we can simply loop over the bunch of fields and retrieve values and labels.
In order to render this fields, the one (read a little bit ugly) solution would be to utilize get_class function:
switch ($class = get_class($field)) {
case 'TextField':
$this->renderTextField($field);
break;
case 'InputField':
$this->renderInputField($field);
break;
// ...
default:
throw new Exception("Cannot render $class.");
}

Answer 4

You are changing label property of $property ('textfield') not $this. It means var_dump($field->textfield->label); doesn't contain anything but var_dump($field->label); does.
Saying that you need to store $property's name so that later you can refer to it. A quick working solution would be:
<?php
class Field
{
public $label;
public $propName;
public function setValue($property, $value)
{
$this->propName = $property;
$this->$property = new \stdClass();
$this->$property->value = $value;
$this->$property->label = $this->label;
return $this;
}
public function setLabel($label)
{
$this->{$this->propName}->label = $label;
}
}
$field = new Field;
$field->setValue('textfield', 'something to print')->setLabel('Label here');
var_dump($field->textfield->value, $field->textfield->label);
Live demo

Answer 5

Sorry to necromance but I wanted to do the same thing but without creating methods for each, while staying nice and short (i didn't want ->setMethod('propertyName', $value))
class Field
{
public function __call($property, $args): self
{
$this->{$property} = $args[0];
return $this;
}
}
Sample use:
$field = (new Field)->label('label!')->value('value!');
And the value of $field:
Field Object
(
[label] => label!
[value] => value!
)
I also whitelisted what property names I'll allow to be set, and just ignore anything else.

Answer 6

In your code "label" has the value into Field Object and not into textfield object as you can see:
Field object {
label => (string) Label here
textfield => stdClass object {
value => (string) something to print
label => null
}
}
You colud use $field->label, because they are stored in different object, or try this:
class Field {
public function setValue($value) {
$this->property = new \stdClass();
$this->property->value = $value;
return $this;
}
public function setLabel($label) {
$this->property->label = $label;
return $this->property;
}
}
$field = new Field();
$field->setValue('something to print')->setLabel('Label here');
print $field->property->value;
print $field->property->label;
Output
something to printLabel here