From 20cb57b1aceacf251f15e553b8082d8ed258b1a1 Mon Sep 17 00:00:00 2001
From: Jinzhu <wosmvp@gmail.com>
Date: Wed, 20 May 2020 02:03:43 +0800
Subject: [PATCH] Add association Delete support

---
 association.go  | 90 +++++++++++++++++++++++++++++++++++++++++++++++++
 schema/utils.go | 15 +++++++++
 2 files changed, 105 insertions(+)

diff --git a/association.go b/association.go
index 82a2274e..027f327e 100644
--- a/association.go
+++ b/association.go
@@ -2,9 +2,11 @@ package gorm
 
 import (
 	"fmt"
+	"reflect"
 
 	"github.com/jinzhu/gorm/clause"
 	"github.com/jinzhu/gorm/schema"
+	"github.com/jinzhu/gorm/utils"
 )
 
 // Association Mode contains some helper methods to handle relationship things easily.
@@ -46,6 +48,90 @@ func (association *Association) Replace(values ...interface{}) error {
 }
 
 func (association *Association) Delete(values ...interface{}) error {
+	if association.Error == nil {
+		var (
+			tx           = association.DB
+			rel          = association.Relationship
+			reflectValue = tx.Statement.ReflectValue
+			conds        = rel.ToQueryConditions(reflectValue)
+			relFields    []*schema.Field
+			foreignKeys  []string
+			updateAttrs  = map[string]interface{}{}
+		)
+
+		for _, ref := range rel.References {
+			if ref.PrimaryValue == "" {
+				if rel.JoinTable == nil || !ref.OwnPrimaryKey {
+					if ref.OwnPrimaryKey {
+						relFields = append(relFields, ref.ForeignKey)
+					} else {
+						relFields = append(relFields, ref.PrimaryKey)
+					}
+
+					foreignKeys = append(foreignKeys, ref.ForeignKey.DBName)
+					updateAttrs[ref.ForeignKey.DBName] = nil
+				}
+			}
+		}
+
+		relValuesMap, relQueryValues := schema.GetIdentityFieldValuesMapFromValues(values, relFields)
+		column, values := schema.ToQueryValues(foreignKeys, relQueryValues)
+		tx.Where(clause.IN{Column: column, Values: values})
+
+		switch association.Relationship.Type {
+		case schema.HasOne, schema.HasMany:
+			modelValue := reflect.New(rel.FieldSchema.ModelType).Interface()
+			tx.Model(modelValue).Clauses(clause.Where{Exprs: conds}).UpdateColumns(updateAttrs)
+		case schema.BelongsTo:
+			tx.Clauses(clause.Where{Exprs: conds}).UpdateColumns(updateAttrs)
+		case schema.Many2Many:
+			modelValue := reflect.New(rel.JoinTable.ModelType).Interface()
+			tx.Clauses(clause.Where{Exprs: conds}).Delete(modelValue)
+		}
+
+		if tx.Error == nil {
+			cleanUpDeletedRelations := func(data reflect.Value) {
+				if _, zero := rel.Field.ValueOf(data); !zero {
+					fieldValue := reflect.Indirect(rel.Field.ReflectValueOf(data))
+
+					fieldValues := make([]reflect.Value, len(relFields))
+					switch fieldValue.Kind() {
+					case reflect.Slice, reflect.Array:
+						validFieldValues := reflect.Zero(rel.Field.FieldType)
+						for i := 0; i < fieldValue.Len(); i++ {
+							for idx, field := range relFields {
+								fieldValues[idx] = field.ReflectValueOf(fieldValue.Index(i))
+							}
+
+							if _, ok := relValuesMap[utils.ToStringKey(fieldValues...)]; !ok {
+								validFieldValues = reflect.Append(validFieldValues, fieldValue.Index(i))
+							}
+						}
+
+						rel.Field.Set(data, validFieldValues)
+					case reflect.Struct:
+						for idx, field := range relFields {
+							fieldValues[idx] = field.ReflectValueOf(data)
+						}
+						if _, ok := relValuesMap[utils.ToStringKey(fieldValues...)]; ok {
+							rel.Field.Set(data, reflect.Zero(rel.FieldSchema.ModelType))
+						}
+					}
+				}
+			}
+
+			switch reflectValue.Kind() {
+			case reflect.Slice, reflect.Array:
+				for i := 0; i < reflectValue.Len(); i++ {
+					cleanUpDeletedRelations(reflect.Indirect(reflectValue.Index(i)))
+				}
+			case reflect.Struct:
+				cleanUpDeletedRelations(reflectValue)
+			}
+		} else {
+			association.Error = tx.Error
+		}
+	}
 	return association.Error
 }
 
@@ -61,6 +147,10 @@ func (association *Association) Count() (count int) {
 		)
 
 		if association.Relationship.JoinTable != nil {
+			for _, queryClause := range association.Relationship.JoinTable.QueryClauses {
+				tx.Clauses(queryClause)
+			}
+
 			tx.Clauses(clause.From{Joins: []clause.Join{{
 				Table: clause.Table{Name: association.Relationship.JoinTable.Table},
 				ON:    clause.Where{Exprs: conds},
diff --git a/schema/utils.go b/schema/utils.go
index 7a26332d..72bd149c 100644
--- a/schema/utils.go
+++ b/schema/utils.go
@@ -128,6 +128,21 @@ func GetIdentityFieldValuesMap(reflectValue reflect.Value, fields []*Field) (map
 	return dataResults, results
 }
 
+// GetIdentityFieldValuesMapFromValues get identity map from fields
+func GetIdentityFieldValuesMapFromValues(values []interface{}, fields []*Field) (map[string][]reflect.Value, [][]interface{}) {
+	resultsMap := map[string][]reflect.Value{}
+	results := [][]interface{}{}
+
+	for _, v := range values {
+		rm, rs := GetIdentityFieldValuesMap(reflect.Indirect(reflect.ValueOf(v)), fields)
+		for k, v := range rm {
+			resultsMap[k] = append(resultsMap[k], v...)
+		}
+		results = append(results, rs...)
+	}
+	return resultsMap, results
+}
+
 // ToQueryValues to query values
 func ToQueryValues(foreignKeys []string, foreignValues [][]interface{}) (interface{}, []interface{}) {
 	queryValues := make([]interface{}, len(foreignValues))