英文:
Golang GORM invalid association
问题
我正在尝试使用GORM编写一个非常简单的belongsTo关联，但是使用的是非Id主键。
我的结构如下：
type State struct {
FIPS string `gorm:"type:char(2);primary_key;column:FIPS"`
Name string `gorm:"not null"`
Area float64 `gorm:"type:real;not null"`
}
type ZipCode struct {
ZipCode string `gorm:"type:char(5);primary_key;"`
Name string `gorm:"not null"`
State State `gorm:"ForeignKey:StateFIPS;AssociationForeignKey:FIPS"`
StateFIPS string `gorm:"type:char(2);column:state_FIPS;not null"`
}
并且使用以下代码：
var zc ZipCode
var s State
db.Model(&zc).Related(&s)
我得到错误：[2017-05-18 14:26:13] invalid association []，并且在对zipcode进行查找时不会加载state。GORM是否不支持非Id主键，或者我漏掉了什么？
英文:
I'm trying to write a very simple belongsTo association with GORM, but with primary keys that isn't Id.
My structs are as such:
type State struct {
FIPS string `gorm:"type:char(2);primary_key;column:FIPS"`
Name string `gorm:"not null"`
Area float64 `gorm:"type:real;not null"`
}
type ZipCode struct {
ZipCode string `gorm:"type:char(5);primary_key;"`
Name string `gorm:"not null"`
State State `gorm:"ForeignKey:StateFIPS;AssociationForeignKey:FIPS"`
StateFIPS string `gorm:"type:char(2);column:state_FIPS;not null"`
}
and with the following code:
var zc ZipCode
var s State
db.Model(&zc).Related(&s)
I get the error: [2017-05-18 14:26:13] invalid association [] and a find on the zipcode doesn't load the state. Does GORM not like non-Id primary keys or am I missing something?
答案1
得分: 0
根据你当前的代码：
var zc ZipCode
var s State
db.Model(&zc).Related(&s)
你没有给zc变量设置任何值，这就是为什么你会得到一个invalid association []的错误，因为数据为空。
要解决这个问题，你需要从数据库中获取ZipCode的数据，例如：
db.First(&zc, 1) // 查找id为1的ZipCode
然后你可以关联zc，完整的代码如下：
var zc ZipCode
var s State
db.First(&zc, 1) // 查找id为1的ZipCode
db.Model(&zc).Related(&s)
注意：我没有测试这段实际的代码，但我认为它可以解决问题。
英文:
With your current code :
var zc ZipCode
var s State
db.Model(&zc).Related(&s)
You are not set anything to your zc variable. so that's why you get an error of invalid association [] with an empty data.
To fix this you must get the ZipCode data from your database like :
db.First(&zc, 1) // find ZipCode with id 1.
and then you can associate your zc full code would be :
var zc ZipCode
var s State
db.First(&zc, 1) // find ZipCode with id 1.
db.Model(&zc).Related(&s)
Note : I'm not testing this actual code but I think it would fix the problem.
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