introduce ability to append a summary row to a datatable

Author: Herbert Maschke

README.md

@@ -158,7 +158,10 @@ class ComplexDemoTable extends LivewireDatatable
 
             (new LabelColumn())
                 ->label('My custom heading')
-                ->content('This fixed string appears in every row')
+                ->content('This fixed string appears in every row'),
+
+            NumberColumn::name('dollars_spent')
+                ->enableSummary(),
         ];
     }
 }
@@ -238,6 +241,23 @@ public function columns()
             ->label('Planet'),
 ```
 
+### Summary row
+If you need to summarize all cells of a specific column, you can use `enableSummary()`:
+
+```php
+public function columns()
+{
+    return [
+        Column::name('dollars_spent')
+            ->label('Expenses in Dollar')
+            ->enableSummary(),
+
+        Column::name('euro_spent')
+            ->label('Expenses in Euro')
+            ->enableSummary(),
+```
+
+
 ### Custom column names
 It is still possible to take full control over your table, you can define a ```builder``` method using whatever query you like, using your own joins, groups whatever, and then name your columns using your normal SQL syntax:
 

resources/views/livewire/datatables/datatable.blade.php

@@ -154,6 +154,20 @@ class="px-3 py-2 border border-green-400 rounded-md bg-white text-green-500 text
                             {{ __("There's Nothing to show at the moment") }}
                         </p>
                     @endforelse
+
+                    @if ($this->hasSummaryRow())
+                        <div class="table-row p-1">
+                            @foreach($this->columns as $column)
+                                @if ($column['summary'])
+                                    <div class="table-cell px-6 py-2 whitespace-no-wrap @if($column['align'] === 'right') text-right @elseif($column['align'] === 'center') text-center @else text-left @endif {{ $this->cellClasses($row, $column) }}">
+                                        {{ $this->summarize($column['name']) }}
+                                    </div>
+                                @else
+                                    <div class="table-cell"></div>
+                                @endif
+                            @endforeach
+                        </div>
+                    @endif
                 </div>
             </div>
         </div>

src/Column.php

@@ -33,6 +33,12 @@ class Column
     public $width;
     public $exportCallback;
 
+    /**
+     * @var bool should the sum of all summarizable cells in this column be
+     *           displayed as a summary at the bottom of the table?
+     */
+    public $summary = false;
+
     /**
      * @var string (optional) you can group your columns to let the user toggle the visibility of a group at once.
      */
@@ -113,6 +119,20 @@ public function label($label)
         return $this;
     }
 
+    public function enableSummary()
+    {
+        $this->summary = true;
+
+        return $this;
+    }
+
+    public function disableSummary()
+    {
+        $this->summary = false;
+
+        return $this;
+    }
+
     public function sortBy($column)
     {
         $this->sort = $column;

src/Http/Livewire/LivewireDatatable.php

@@ -202,6 +202,7 @@ public function getViewColumns()
                 'hidden',
                 'label',
                 'group',
+                'summary',
                 'content',
                 'align',
                 'type',
@@ -617,6 +618,34 @@ public function getSortString()
         }
     }
 
+    /**
+     * @return bool has the user defined at least one column to display a summary row?
+     */
+    public function hasSummaryRow()
+    {
+        foreach ($this->columns as $column) {
+            if ($column['summary']) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    /**
+     * Attempt so summarize each data cell of the given column.
+     * In case we have a string or any other value that is not summarizable,
+     * we return a empty string.
+     */
+    public function summarize($column)
+    {
+        try {
+            return $this->results->sum($column);
+        } catch (\TypeError $e) {
+            return '';
+        }
+    }
+
     public function updatingPerPage()
     {
         $this->refreshLivewireDatatable();