Readability update

Small readability update. Includes also a switch from bool return values to
error return values in Scope.SetColumn and Field.Set.

field.go

@@ -2,6 +2,7 @@ package gorm
 
 import (
 	"database/sql"
+	"errors"
 	"reflect"
 	"time"
 )
@@ -35,9 +36,15 @@ func (field *Field) IsTime() bool {
 	return isTime
 }
 
-func (field *Field) Set(value interface{}) (result bool) {
-	if field.Field.IsValid() && field.Field.CanAddr() {
-		result = true
+func (field *Field) Set(value interface{}) (err error) {
+	if !field.Field.IsValid() {
+		return errors.New("field value not valid")
+	}
+
+	if !field.Field.CanAddr() {
+		return errors.New("field value not addressable")
+	}
+
 	if rvalue, ok := value.(reflect.Value); ok {
 		value = rvalue.Interface()
 	}
@@ -47,11 +54,10 @@ func (field *Field) Set(value interface{}) (result bool) {
 	} else if reflect.TypeOf(value).ConvertibleTo(field.Field.Type()) {
 		field.Field.Set(reflect.ValueOf(value).Convert(field.Field.Type()))
 	} else {
-			result = false
+		return errors.New("could not convert argument")
 	}
-	}
-	if result {
+
 	field.IsBlank = isBlank(field.Field)
-	}
+
 	return
 }

scope.go

@@ -129,19 +129,18 @@ func (scope *Scope) PrimaryKeyValue() interface{} {
 }
 
 // HasColumn to check if has column
-func (scope *Scope) HasColumn(column string) bool {
+func (scope *Scope) HasColumn(column string) (hasColumn bool) {
 	clone := scope
 	if scope.IndirectValue().Kind() == reflect.Slice {
 		value := reflect.New(scope.IndirectValue().Type().Elem()).Interface()
 		clone = scope.New(value)
 	}
 
-	for _, field := range clone.Fields(false) {
-		if field.Name == column || field.DBName == column {
-			return true
-		}
-	}
-	return false
+	dbName := ToSnake(column)
+
+	_, hasColumn = clone.Fields(false)[dbName]
+
+	return
 }
 
 // FieldValueByName to get column's value and existence
@@ -150,20 +149,21 @@ func (scope *Scope) FieldValueByName(name string) (interface{}, bool) {
 }
 
 // SetColumn to set the column's value
-func (scope *Scope) SetColumn(column interface{}, value interface{}) bool {
+func (scope *Scope) SetColumn(column interface{}, value interface{}) error {
 	if field, ok := column.(*Field); ok {
 		return field.Set(value)
 	} else if str, ok := column.(string); ok {
 		if scope.Value == nil {
-			return false
+			return errors.New("scope value must not be nil for string columns")
 		}
-		for _, field := range scope.Fields() {
-			if field.Name == str || field.DBName == str {
+
+		dbName := ToSnake(str)
+
+		if field, ok := scope.Fields()[dbName]; ok {
 			return field.Set(value)
 		}
 	}
-	}
-	return false
+	return errors.New("could not convert column to field")
 }
 
 // CallMethod invoke method with necessary argument