my changes

app/Book.php

@@ -1,51 +1,50 @@
-<?php namespace App;
+<?php
+namespace App;
 
 use Illuminate\Database\Eloquent\Model;
 
-class Book extends Model {
+class Book extends Model
+{
+    protected $table = 'books';
 
-	protected $fillable = [
-		'title',
-		'author',
-		'year',
-		'stock',
-		'category_id',
-		'shelf_id'
-	];
+    protected $fillable = [
+        'title',
+        'author',
+        'year',
+        'stock',
+        'project_id'
+    ];
 
-	public function category()
-	{
-	
-		return $this->belongsTo('App\Category');
-	
-	}
+    public function project()
+    {
+        return $this->belongsTo('App\Project', 'project_id', 'id');
+    }
 
-	public function shelf()
-	{
-	
-		return $this->belongsTo('App\Shelf');
-	
-	}
+    // public function shelf()
+    // {
+    // return $this->belongsTo('App\Shelf');
+    // }
 
-	public function transactions()
-	{
+    public function transactions()
+    {
+        //model, foreign key on the Transaction model is book_id, local id
+        return $this->hasMany('App\Transaction', 'book_id', 'id');
+    }
 
-		return $this->hasMany('App\Transaction');
 
-	}
 
-	public function scopeAvailable($query)
-	{
-		
-		return $query->where('stock', '>', 0);
+    public function scopeAvailable($query)
+    {
+        return $query->where('stock', '>', 0);
+    }
 
-	}
-
-	public function scopeOrderByTitle($query)
-	{
-		
-		return $query->orderBy('title');
-
-	}
+    public function scopeOrderByTitle($query)
+    {
+        return $query->orderBy('title');
+    }
 
+    public function hasProject()
+    {
+        return $this->project()->exists();
+    }
 }