dynamic-struct/builder.go

package dynamicstruct

import "reflect"

type (
	// Builder 运行时动态生成结构体的接口约束
	Builder interface {
		// AddField 添加结构体字段
		AddField(name string, pkg string, typ any, tag string, anonymous bool) Builder
		// RemoveField 移除指定名称的结构体字段
		RemoveField(name string) Builder
		// HasField 检测指定名称的结构体字段是否存在
		HasField(name string) bool
		// GetField 根据名称获取结构体字段定义
		GetField(name string) FieldConfig
		// Build 返回动态定义的结构体.
		Build() DynamicStruct
	}

	// FieldConfig 结构体字段的定义.
	FieldConfig interface {
		// SetType 设置字段类型.
		SetType(typ any) FieldConfig
		// SetTag 设置字段 tag.
		SetTag(tag string) FieldConfig
	}

	// DynamicStruct contains defined dynamic struct.
	// This definition can't be changed anymore, once is built.
	// It provides a method for creating new instances of same defintion.
	DynamicStruct interface {
		// New 获取结构体实例, 所有字段值均为对应类型的初始零值
		New() any

		// NewSliceOfStructs slice实例化
		NewSliceOfStructs() any

		// NewMapOfStructs map 或者 struct实例化
		NewMapOfStructs(key any) any
	}

	builderImpl struct {
		fields []*fieldConfigImpl
	}

	fieldConfigImpl struct {
		name      string
		pkg       string
		typ       any
		tag       string
		anonymous bool
	}

	dynamicStructImpl struct {
		definition reflect.Type
	}
)

// NewStruct 获取builder实例
func NewStruct() Builder {
	return &builderImpl{
		fields: []*fieldConfigImpl{},
	}
}

// ExtendStruct 基于已有结构体, 生成动态结构体(相当于继承指定的结构体属性)
func ExtendStruct(value ...any) Builder {
	return MergeStructs(value...)
}

// MergeStructs 多个结构体合并成一个动态结构体
func MergeStructs(values ...any) Builder {
	builder := NewStruct()

	for _, value := range values {
		valueOf := reflect.Indirect(reflect.ValueOf(value))
		typeOf := valueOf.Type()

		for i := 0; i < valueOf.NumField(); i++ {
			fVal := valueOf.Field(i)
			fTyp := typeOf.Field(i)
			builder.(*builderImpl).AddField(fTyp.Name, fTyp.PkgPath, fVal.Interface(), string(fTyp.Tag), fTyp.Anonymous)
		}
	}

	return builder
}

// AddField 添加结构体字段
func (b *builderImpl) AddField(name string, pkg string, typ any, tag string, anonymous bool) Builder {
	if existFieldCfg := b.GetField(name); nil != existFieldCfg {
		// 说明已存在指定名称字段
		// 重复添加, 则会议后面的标签以及类型, 覆盖前面的值
		existFieldCfg.SetTag(tag)
		existFieldCfg.SetType(typ)
		return b
	}
	b.fields = append(b.fields, &fieldConfigImpl{
		name:      name,
		typ:       typ,
		tag:       tag,
		anonymous: anonymous,
		pkg:       pkg,
	})
	return b
}

// RemoveField 根据名称移除结构体字段
func (b *builderImpl) RemoveField(name string) Builder {
	newFieldList := make([]*fieldConfigImpl, 0)
	for i := range b.fields {
		if b.fields[i].name == name {
			continue
		}
		newFieldList = append(newFieldList, b.fields[i])
	}
	b.fields = newFieldList
	return b
}

// HasField 是否存在指定字段
func (b *builderImpl) HasField(name string) bool {
	for i := range b.fields {
		if b.fields[i].name == name {
			return true
		}
	}
	return false
}

// GetField 根据名称获取字段配置, 不存在, 返回nil
func (b *builderImpl) GetField(name string) FieldConfig {
	for i := range b.fields {
		if b.fields[i].name == name {
			return b.fields[i]
		}
	}
	return nil
}

// Build 构建动态结构体
func (b *builderImpl) Build() DynamicStruct {
	var structFields []reflect.StructField

	for _, field := range b.fields {
		structFields = append(structFields, reflect.StructField{
			Name:      field.name,
			PkgPath:   field.pkg,
			Type:      reflect.TypeOf(field.typ),
			Tag:       reflect.StructTag(field.tag),
			Anonymous: field.anonymous,
		})
	}

	return &dynamicStructImpl{
		definition: reflect.StructOf(structFields),
	}
}

// SetType 设置字段类型
func (f *fieldConfigImpl) SetType(typ any) FieldConfig {
	f.typ = typ
	return f
}

// SetTag 设置字段标签
func (f *fieldConfigImpl) SetTag(tag string) FieldConfig {
	f.tag = tag
	return f
}

// New 创建动态结构体实例
func (ds *dynamicStructImpl) New() any {
	return reflect.New(ds.definition).Interface()
}

// NewSliceOfStructs 创建动态结构体切片实例
func (ds *dynamicStructImpl) NewSliceOfStructs() any {
	return reflect.New(reflect.SliceOf(ds.definition)).Interface()
}

// NewMapOfStructs 创建动态结构体map实例
func (ds *dynamicStructImpl) NewMapOfStructs(key any) any {
	return reflect.New(reflect.MapOf(reflect.Indirect(reflect.ValueOf(key)).Type(), ds.definition)).Interface()
}