Golang Gorm 一对多 关联模式 Association + Append 添加关联 Association + Replace

添加关联

为 many to many、has many 添加新的关联；为 has one, belongs to 替换当前的关联

db.Model(&user).Association("Languages").Append([]Language{languageZH, languageEN})
 
db.Model(&user).Association("Languages").Append(&Language{Name: "DE"})
 
db.Model(&user).Association("CreditCard").Append(&CreditCard{Number: "411111111111"})

替换关联

用一个新的关联替换当前的关联

db.Model(&user).Association("Languages").Replace([]Language{languageZH, languageEN})
 
db.Model(&user).Association("Languages").Replace(Language{Name: "DE"}, languageEN)
 
	var u User
	db.Take(&u, 1)
	var l Language
	db.Take(&l, 3)
	db.Model(&u).Association("Languages").Replace(&l)

删除关联   删除中间表数据

如果存在，则删除源模型与参数之间的关系，只会删除引用，不会从数据库中删除这些对象。 

db.Model(&user).Association("Languages").Delete([]Language{languageZH, languageEN})
db.Model(&user).Association("Languages").Delete(languageZH, languageEN)