original_string: private function _prepareColumns(array $columnArray)
  	{
  		if(count($columnArray) === 0)
  		{
  			throw new \Exception('The column method of the statement must called before!');
  		}
  		foreach($columnArray as $column)
  		{
  			$this->columns .= $column->getColumnName() . ', ';
  		}
  		$this->columns = rtrim($this->columns);
  		$this->columns = rtrim($this->columns, ',');
  
  		return $this;
  	}
code: private function _prepareColumns(array $columnArray)
  	{
  		if(count($columnArray) === 0)
  		{
  			throw new \Exception('The column method of the statement must called before!');
  		}
  		foreach($columnArray as $column)
  		{
  			$this->columns .= $column->getColumnName() . ', ';
  		}
  		$this->columns = rtrim($this->columns);
  		$this->columns = rtrim($this->columns, ',');
  
  		return $this;
  	}
code_tokens: private function _prepareColumns ( array $ columnArray ) { if ( count ( $ columnArray ) === 0 ) { throw new \ Exception ( 'The column method of the statement must called before!' ) ; } foreach ( $ columnArray as $ column ) { $ this -> columns .= $ column -> getColumnName ( ) . ', ' ; } $ this -> columns = rtrim ( $ this -> columns ) ; $ this -> columns = rtrim ( $ this -> columns , ',' ) ; return $ this ; }
docstring: Validate and prepare the columns property to set it to the query.
  
  @param ColumnInterface[] $columnArray An array with ColumnInterface objects as elements.
  
  @return $this The same instance to concatenate methods.
  @throws \Exception When column method of statement was not invoked.
docstring_tokens: Validate and prepare the columns property to set it to the query .