Issue #7 Make writer object accessible

Author: mikehaertl

README.md

@@ -47,13 +47,14 @@ Find more examples below.
 
 Property | Description
 ---------|-------------
-`writer` | The file format as supported by PHPOffice. The default is ` '\PHPExcel_Writer_Excel2007'`
+`writerClass` | The file format as supported by PHPOffice. The default is ` '\PHPExcel_Writer_Excel2007'`
 `sheets` | An array of sheet configurations (see below). The keys are used as sheet names.
 
 Methods | Description
 ---------|-------------
 `saveAs($name)` | Saves the excel file under `$name`
 `send($name=null,$inline=false)` | Sends the excel file to the browser. If `$name` is empty, the file is streamed for inline display, otherwhise a download dialog will open, unless `$inline` is `true` which will force inline display even if a filename is supplied.
+`getWriter()` | Returns the `PHPExcel_Writer_Abstract` instance
 `getWorkbook()` | Returns the `PHPExcel` workbook instance
 `getTmpFile()` | Returns the `mikehaertl\tmp\File` instance of the temporary file
 
@@ -93,7 +94,7 @@ Property | Description
 $file = \Yii::createObject([
     'class' => 'codemix\excelexport\ExcelFile',
 
-    'writer' => '\PHPExcel_Writer_Excel5', // Override default of `\PHPExcel_Writer_Excel2007`
+    'writerClass' => '\PHPExcel_Writer_Excel5', // Override default of `\PHPExcel_Writer_Excel2007`
 
     'sheets' => [
 

src/ExcelFile.php

@@ -13,13 +13,26 @@ class ExcelFile extends Object
     /**
      * @var string the writer class to use. Default is `\PHPExcel_Writer_Excel2007`.
      */
-    public $writer = '\PHPExcel_Writer_Excel2007';
+    public $writerClass = '\PHPExcel_Writer_Excel2007';
 
+    protected $_writer;
     protected $_workbook;
     protected $_sheets;
     protected $_tmpFile;
     protected $_created = false;
 
+    /**
+     * @return PHPExcel_Writer_Abstract the writer instance
+     */
+    public function getWriter()
+    {
+        if ($this->_writer===null) {
+            $class = $this->writerClass;
+            $this->_writer = new $class($this->getWorkbook());
+        }
+        return $this->_writer;
+    }
+
     /**
      * @return PHPExcel the workbook instance
      */
@@ -108,9 +121,7 @@ protected function createFile()
                 }
                 Yii::createObject($config, [$sheet])->render();
             }
-            $class = $this->writer;
-            $writer = new $class($workbook);
-            $writer->save((string) $this->getTmpFile());
+            $this->getWriter()->save((string) $this->getTmpFile());
             $this->_created = true;
         }
     }