Select statement execution and mapping to struct or slice added.

sqlbuilder/execution/execution.go

@@ -0,0 +1,144 @@
+package execution
+
+import (
+	"database/sql"
+	"errors"
+	"github.com/serenize/snaker"
+	"reflect"
+)
+
+func Execute(db *sql.DB, query string, destinationPtr interface{}) error {
+	if db == nil {
+		return errors.New("db is nil")
+	}
+
+	if destinationPtr == nil {
+		return errors.New("Destination is nil ")
+	}
+
+	destinationType := reflect.TypeOf(destinationPtr)
+	if destinationType.Kind() != reflect.Ptr {
+		return errors.New("Destination has to be a pointer to slice or pointer to struct ")
+	}
+
+	rows, err := db.Query(query)
+
+	if err != nil {
+		return err
+	}
+
+	columnNames, _ := rows.Columns()
+	columnTypes, _ := rows.ColumnTypes()
+	values := createScanValue(columnTypes)
+
+	for rows.Next() {
+		err := rows.Scan(values...)
+
+		if err != nil {
+			return err
+		}
+
+		if destinationType.Elem().Kind() == reflect.Slice {
+
+			destinationStructPtr := newElemForSlice(destinationPtr)
+
+			err = mapValuesToStruct(columnNames, values, destinationStructPtr)
+
+			if err != nil {
+				return err
+			}
+
+			appendElemToSlice(destinationPtr, destinationStructPtr)
+		} else if destinationType.Elem().Kind() == reflect.Struct {
+			return mapValuesToStruct(columnNames, values, destinationPtr)
+		}
+	}
+
+	err = rows.Err()
+
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func appendElemToSlice(slice interface{}, obj interface{}) {
+	//spew.Dump(slice)
+	sliceValue := reflect.ValueOf(slice).Elem()
+
+	sliceValue.Set(reflect.Append(sliceValue, reflect.ValueOf(obj).Elem()))
+}
+
+func newElemForSlice(destinationSlicePtr interface{}) interface{} {
+	destinationSliceType := reflect.TypeOf(destinationSlicePtr).Elem()
+
+	return reflect.New(destinationSliceType.Elem()).Interface()
+}
+
+func mapValuesToStruct(columnNames []string, row []interface{}, destination interface{}) error {
+	structType := reflect.TypeOf(destination).Elem()
+	structValue := reflect.ValueOf(destination).Elem()
+
+	for i := 0; i < structType.NumField(); i++ {
+		fieldType := structType.Field(i)
+		fieldValue := structValue.Field(i)
+
+		fieldName := fieldType.Name
+
+		//columnName := structName + "." + fieldName
+		columnName := snaker.CamelToSnake(fieldName)
+
+		rowIndex := getIndex(columnNames, columnName)
+
+		if rowIndex < 0 {
+			continue
+		}
+
+		rowColumnValue := reflect.ValueOf(row[rowIndex])
+
+		setReflectValue(rowColumnValue, fieldValue)
+	}
+
+	return nil
+}
+
+func setReflectValue(source, destination reflect.Value) {
+	if destination.Kind() == reflect.Ptr {
+		if source.Kind() == reflect.Ptr {
+			destination.Set(source)
+		} else {
+			destination.Set(source.Addr())
+		}
+	} else {
+		if source.Kind() == reflect.Ptr {
+			destination.Set(source.Elem())
+		} else {
+			destination.Set(source)
+		}
+	}
+}
+
+func getIndex(list []string, text string) int {
+	for i, str := range list {
+		if str == text {
+			return i
+		}
+	}
+
+	return -1
+}
+
+func createScanValue(columnTypes []*sql.ColumnType) []interface{} {
+	values := make([]interface{}, len(columnTypes))
+
+	for i, sqlColumnType := range columnTypes {
+		columnType := sqlColumnType.ScanType()
+
+		columnValue := reflect.New(columnType)
+
+		values[i] = columnValue.Interface()
+	}
+
+	return values
+}