更新方法不更新零值 [英] Update method does not update zero value

问题描述

原始问题

在GORM中使用 Update 方法时，不会保存新数据.即我想将 bool 从 true 设置为 false ，但是即使在 Update 方法之后，它仍然保持为true.

When using the Update method in GORM the new data does not get saved. i.e. I want to set a bool from true to false, but it stays true even after the Update method.

在该方法的说明中有一个警告:警告，当用struct更新时，GORM不会更新值为零的字段"

In the description of the method there is a warning: "WARNING when update with struct, GORM will not update fields that with zero value"

由于我使用结构进行更新并且 false 是 bool 的零值，因此这似乎是预期的行为，但是我看不出为什么要这样做那么，以及如何克服这个问题.

Since I am using a struct to update and false is the zero value of bool, this seems expected behaviour, but I don't see any reason why to do so and how to overcome this.

func UpdateData(c *fiber.Ctx) error {
    db := database.DBConn

    data := new([]entities.Data)

    if err := c.BodyParser(&data); err != nil {
        return err
    }

    db.Update(&data)
    return c.JSON(data)
}

解决方案摘要

首先，根据建议，我在实例化结构时省略了 new 关键字.然后，我使用了一个辅助函数(来自此处)，用于将结构转换为映射，同时将json别名保留为键:

First, as suggested I left out the new keyword when instantiating the structs. Then, I used a helper function (from here) for converting a struct to map while keeping the json alias as keys:

// StructToMap Converts a struct to a map while maintaining the json alias as keys
func StructToMap(obj interface{}) (newMap map[string]interface{}, err error) {
    data, err := json.Marshal(obj)

    if err != nil {
        return
    }

    err = json.Unmarshal(data, &newMap) // Convert to a map
    return
}

然后，我遍历数据切片中的每个元素，以便对其进行转换并一次更新:

Then I loop over each element in the data slice in order to convert it and update it one by one:

func UpdateData(c *fiber.Ctx) error {
    db := database.DBConn

    data := []entities.Dard{}

    if err := c.BodyParser(&data); err != nil {
        return err
    }

    for _, record := range data {
        mappedData, _ := StructToMap(record)
        db.Model(&entities.Data{}).Update(mappedData)
    }

    return c.JSON(data)
}

*在此示例中，错误处理明显减少了.

*Error handling is obviously reduced in this example.

推荐答案

摘自官方 doc

注意使用struct更新时，GORM将仅更新非零值字段，您可能希望使用地图来更新属性或使用选择"指定要更新的字段

NOTE When update with struct, GORM will only update non-zero fields, you might want to use map to update attributes or use Select to specify fields to update

因此，请使用 map [string] interface {} 来更新非零字段.示例:

So use map[string]interface{} to update non-zero fields also. Example:

db.Model(&user).Updates(map[string]interface{}{"name": "hello", "age": 18, "actived": false})

已经有了结构，您可以将 struct 转换为 map [string] interface {} (

As you have struct already you can convert struct into map[string]interface{} (See details about conversion) then update. Another way is change the type of field as pointer.

这篇关于更新方法不更新零值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！