Laravel ORM dynamic model attributes - php

Question

I have a database set up that I am not sure how to code in laravel. I am trying to basically get dynamic attribute names from custom input.
Here's the DB setup:
Category:
-ID
-Name
Product:
-ID
-Category_id
Product_Attribute:
-ID
-Category_id
-Attribute_Name
Attribute_value:
-ID
-Product_id
-Product_attribute_id
-Value
There can be multiple values for each attribute and I don't have a set list of attributes as it can change depending on the category/product. Some products have some attributes and some don't. Some will have the same key/name as in other categories but will rarely overlap for my purposes but i can work around that if need be.
I there a way to setup laravel so i can look through the keys / values as well as call them by name
echo $product->$Attribute_Name;
or
echo $product->attributes[$Attribute_Name];
or something similar
but i also need to pull all products where attribute name = y and attribute Value = X
select * from Products join Attribute_value on products.ID = Attribute_value.Product_id join Product_Attribute on Category_id = Products.Category_id and Product_Attribute.ID = Attribute_value.Product_attribute_id where Product_Attribute = '{attribute_name}' and Attribute_value = '{Attribute_value}'
This is only return the products but not with the associated data or the other attributes. I can't find and easy way of loading that data without having to build a class to populate it. Ideally I would like to be able to change the values and save them using the ORM similar to how a one to many relationship works.
I have seen this type of structure before in databases. I was wondering if there was a way to do this easily in laravel without having to create a bunch of custom functions to load the attributes for each product.
Thanks

Answer 1

I'm a little confused by your question, but what you first want to do is create all the models and relationships. You don't necessarily need a model for each of the four tables, but I'd strongly recommend it.
class Category
{
public function products(): HasMany
{
return $this->hasMany(Product::class);
}
public function productAttributes(): HasMany
{
return $this->hasMany(ProductAttribute::class);
}
}
class Product
{
public function category(): BelongsTo
{
return $this->belongsTo(Category::class);
}
public function attributeValues(): HasMany
{
return $this->hasMany(AttributeValue::class);
}
}
class ProductAttribute
{
public function category(): BelongsTo
{
return $this->belongsTo(Category::class);
}
public function attributeValues(): HasMany
{
return $this->hasMany(AttributeValue::class);
}
}
class AttributeValue
{
public function product(): BelongsTo
{
return $this->belongsTo(Product::class);
}
public function productAttribute(): BelongsTo
{
return $this->belongsTo(ProductAttribute::class);
}
}
This code expects you to consider the Laravel naming standards of tables and properties.
After defining the classes and relationships, you may load products with their attributes like this:
$products = Product::query()
->with('attributeValues.productAttribute')
->where('category_id', $categoryId)
->get();
Because this makes accessing an attribute by it's name a pain...
$product = $products->first();
$color = optional($product->attributeValues
->where('productAttribute.name', 'color')
->first())->value ?? 'white';
... you can also override the __get($name) method to add a nice accessor for your attributes:
class Product
{
public function __get(string $name)
{
if ($name === 'attrs') {
return (object) $this->attributeValues->mapWithKeys(function ($attributeValue) {
return [$attributeValue->productAttribute->name => $attributeValue->value];
});
}
return parent::__get($name);
}
}
After doing so, you should be able to access your attributes like this:
$product = $products->first();
$color = $product->attrs->color;
// or if you need to retrieve an attribute by name stored in a variable
$name = 'color';
$attr = $product->attrs->$name;
Of course you can also omit the (object) cast in the __get($name) accessor to return an array instead. You then receive this syntax: $product->attrs['color']. Either way, this will return an error if a property is not set / not in the array. Make sure to catch this. You may also want to add some caching to avoid building the attrs object/array over and over again.
Please note: The $attributes property is used by the Eloquent base model internally to store all the properties of a model. So this name is reserved and you should use something else like attrs instead.
Edit: Two more options for getters would be the following ones:
class Product
{
public function getColorAttribute(string $default = 'white'): string
{
return optional($this->attributeValues
->where('productAttribute.name', 'color')
->first())->value ?? $default;
}
public function getAttr(string $name, $default = null)
{
return optional($this->attributeValues
->where('productAttribute.name', $name)
->first())->value ?? $default;
}
}
Similarly, you could design a setter:
class Product
{
public function setAttr(string $name, $value): void
{
if ($this->hasAttr($name)) {
$attr = $this->attributeValues
->where('productAttribute.name', $name)
->first();
$attr->value = $value;
$attr->save();
} else {
throw new \Exception(sprintf('This product may not have the attribute [%s].', $name));
}
}
public function hasAttr(string $name): bool
{
return $this->attributeValues
->contains('productAttribute.name', $name);
}
}