# Relationships
For querying relationships, you can use QuerySeter or QueryM2Mer。
For example：
o := orm.NewOrm()
post := Post{Id: 1}
m2m := o.QueryM2M(&post, "Tags")
// In the first param object must have primary key
// The second param is the M2M field will work with
// API of QueryM2Mer will used to Post with id equals 1
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Full API:
- Add(...interface{}) (int64, error)
- Remove(...interface{}) (int64, error)
- Exist(interface{}) bool
- Clear() (int64, error)
- Count() (int64, error)
# QueryM2Mer Add
tag := &Tag{Name: "golang"}
o.Insert(tag)
num, err := m2m.Add(tag)
if err == nil {
fmt.Println("Added nums: ", num)
}
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Add accepts Tag,*Tag,[]*Tag,[]Tag,[]interface{}。
var tags []*Tag
...
// After reading tags
...
num, err := m2m.Add(tags)
if err == nil {
fmt.Println("Added nums: ", num)
}
// It can pass multiple params
// m2m.Add(tag1, tag2, tag3)
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# QueryM2Mer Remove
Remove tag from M2M relation:
Remove supports many types: Tag *Tag []*Tag []Tag []interface{}
var tags []*Tag
...
// After reading tags
...
num, err := m2m.Remove(tags)
if err == nil {
fmt.Println("Removed nums: ", num)
}
// It can pass multiple params
// m2m.Remove(tag1, tag2, tag3)
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# QueryM2Mer Exist
Test if Tag is in M2M relation
if m2m.Exist(&Tag{Id: 2}) {
fmt.Println("Tag Exist")
}
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# QueryM2Mer Clear
Clear all M2M relation:
nums, err := m2m.Clear()
if err == nil {
fmt.Println("Removed Tag Nums: ", nums)
}
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# QueryM2Mer Count
Count the number of Tags:
nums, err := m2m.Count()
if err == nil {
fmt.Println("Total Nums: ", nums)
}
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