# Panel Go Relationship > Implement database relationships for Panel.go with BelongsTo, HasMany, HasOne, BelongsToMany, and polymorphic relationships. Use when adding relationships between entities or configuring eager loading. See panel-go-plugin-scaffold for comprehensive examples with --with-example flag. Use when this capability is needed. - Skill: `tomevault-io/panel-go-relationship` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/panel-go-relationship` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/panel-go-relationship/raw - Safety review: pending (external: skill-scanner PASS, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/panel-go-relationship --- # Panel.go Relationship Expert Expert in implementing database relationships for Panel.go with BelongsTo, HasMany, HasOne, BelongsToMany, and polymorphic relationships. ## Expertise - **BelongsTo**: One-to-one, child to parent (Post belongs to User) - **HasOne**: One-to-one, parent to child (User has one Profile) - **HasMany**: One-to-many (User has many Posts) - **BelongsToMany**: Many-to-many (Post belongs to many Tags) - **MorphTo**: Polymorphic relationships (Comment belongs to Commentable) - **MorphToMany**: Polymorphic many-to-many (Tag belongs to many Taggables) - **Eager Loading**: Preload, Joins to prevent N+1 - **Entity.go Pattern**: All entities in one file to prevent circular dependency - **Registry Pattern**: Resource access without direct imports ## Quick Patterns ### BelongsTo ```go type Post struct { ID uint UserID uint User *User `gorm:"foreignKey:UserID;constraint:OnUpdate:CASCADE,OnDelete:CASCADE"` } fields.BelongsTo("User", "user_id", resources.GetOrPanic("users")). DisplayUsing("name"). WithSearchableColumns("name", "email"). WithEagerLoad() ``` ### HasMany ```go type User struct { ID uint Posts []Post `gorm:"foreignKey:UserID"` } fields.HasMany("Posts", "posts", resources.GetOrPanic("posts")). ForeignKey("user_id"). OwnerKey("id"). WithEagerLoad() ``` ### HasOne ```go type Organization struct { ID uint BillingInfo *BillingInfo `gorm:"foreignKey:OrganizationID"` } type BillingInfo struct { ID uint OrganizationID uint `gorm:"not null;unique;index"` Organization *Organization } fields.HasOne("BillingInfo", "billing_info", resources.GetOrPanic("billing-info")). ForeignKey("organization_id"). OwnerKey("id"). WithEagerLoad() ``` ### BelongsToMany ```go type Post struct { ID uint Tags []Tag `gorm:"many2many:post_tags;"` } type Tag struct { ID uint Posts []Post `gorm:"many2many:post_tags;"` } fields.BelongsToMany("Tags", "tags", resources.GetOrPanic("tags")). PivotTable("post_tags"). WithEagerLoad() ``` ### MorphTo (Polymorphic) ```go type Comment struct { ID uint CommentableID uint `gorm:"index:idx_commentable"` CommentableType string `gorm:"index:idx_commentable"` Content string } // Entity'de tanımlanır, ancak field henüz implement edilmemiş ``` ### MorphToMany (Polymorphic Many-to-Many) ```go type Tag struct { ID uint Name string } // Taggable pivot table ile Product ve Shipment'a bağlanır // Entity'de tanımlanır, ancak field henüz implement edilmemiş ``` ### Eager Loading ```go func (r *PostResource) With() []string { return []string{"User", "Category", "Tags"} } ``` ## Entity.go Pattern **Tüm entity'leri tek dosyada tut** (circular dependency önlenir): ```go // entity/entity.go package entity type Organization struct { ID uint Addresses []Address // HasMany BillingInfo *BillingInfo // HasOne } type Address struct { ID uint OrganizationID uint Organization *Organization // BelongsTo } type BillingInfo struct { ID uint OrganizationID uint `gorm:"unique"` Organization *Organization // BelongsTo (HasOne) } ``` ## Registry Pattern **Resource'lar birbirini import etmeden erişir**: ```go // resources/registry.go var registry = make(map[string]func() resource.Resource) func Register(slug string, factory func() resource.Resource) { registry[slug] = factory resource.Register(slug, factory()) } func GetOrPanic(slug string) resource.Resource { if r := Get(slug); r != nil { return r } panic("resource not found: " + slug) } // Kullanım fields.HasMany("Addresses", "addresses", resources.GetOrPanic("addresses")) ``` ## Key Rules - **Always index foreign keys** - **Use Preload** to prevent N+1 queries - **Define cascade rules** (CASCADE, RESTRICT, SET NULL) - **Set DisplayKey** for relationships - **Add With()** method for eager loading - **Use entity.go pattern** for all entities - **Use registry pattern** for resource access ## Usage When user asks to add relationships: 1. Add foreign key to entity in `entity/entity.go` 2. Add relationship field with GORM tags 3. Add relationship field to field resolver using `resources.GetOrPanic()` 4. Set DisplayUsing, WithSearchableColumns, WithEagerLoad 5. Add eager loading in With() method ## Comprehensive Examples For comprehensive examples with all relationship types: ```bash panel plugin create example --with-example ``` This creates 9 entities and 7 resources demonstrating: - BelongsTo, HasMany, HasOne, BelongsToMany - MorphTo, MorphToMany (entity level) - Entity.go pattern - Registry pattern See `panel-go-plugin-scaffold` skill for details. ## Anti-Patterns ❌ **Don't forget foreign key indexes** - Always index foreign keys ❌ **Don't skip eager loading** - Use With() to prevent N+1 queries ❌ **Don't forget DisplayUsing** - Set DisplayUsing for relationship fields ❌ **Don't skip cascade rules** - Define OnUpdate and OnDelete behavior ❌ **Don't use wrong field types** - BelongsTo for belongs_to, HasMany for has_many, etc. ❌ **Don't separate entities** - Use entity.go pattern to prevent circular dependency ❌ **Don't import resources directly** - Use registry pattern ## Sharp Edges ⚠️ **N+1 Queries**: Always use WithEagerLoad() for relationships ⚠️ **Cascade Deletes**: Be careful with CASCADE on delete ⚠️ **Many-to-Many**: Requires junction table (many2many tag) ⚠️ **DisplayUsing**: Must match actual field name in related entity ⚠️ **Polymorphic**: MorphTo/MorphToMany fields not yet implemented in panel.go ⚠️ **Circular Dependency**: Use entity.go pattern to prevent import cycles ⚠️ **Registry Timing**: init() functions run on import, order matters --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/ferdiunal) — claim your Tome and manage your conversions.