Explore how to do DTO conversion in Go

Go is an excellent programming language that is widely used in microservices and web development. In Go applications, DTO (Data Transfer Object) conversion is a common problem. This article will explore how to perform DTO conversion in Go.

1. What is DTO

DTO is a general design pattern used to solve data transmission problems in programming languages ​​such as Java and .NET. DTO stands for Data Transfer Object, which is used to transfer data from one layer to another. The data transferred may be data from a database, web service, web form, or other source.

DTO contains simple attributes of data without any business logic. DTO often corresponds to the data structure of a database table or other data source, so the attribute names and types of DTO are based on the database fields and data types.

In Go, DTO is a structure that contains properties of a database table or other data source. The DTO should be lightweight as it is only used for transferring data.

2. Why DTO is needed

In applications, data is usually stored in a database, and web applications need to add, update, delete and retrieve data to the database. There may be many layers in an application, each with different responsibilities. For example, in a web application, there is a layer that represents views, a layer that represents business logic, and a layer that represents data access.

When transmitting data between these layers, the data often needs to be converted. Different layers may require different data structures, and DTO can transmit data using a common data format.

DTO also provides another benefit, which is that it can protect database schema changes. If the DTO has to be changed due to a change in the database schema, then only the DTO needs to be changed and not all the layers that use the DTO.

3. DTO implementation in Go

In Go, DTO can be easily implemented by defining a structure. For example, let's say we have a user accounts table with username and password fields. We can define a UserDTO structure as follows:

type UserDTO struct {
    Username string
    Password string
}

When converting properties from a DTO to an entity object, the properties of the entity object can be set using standard Go struct field assignment. For example, suppose we have a User entity object:

type User struct {
    ID string
    Username string
    Password string
}

We can use the following code to convert UserDTO to User:

userDTO := UserDTO{
    Username: "testuser",
    Password: "testpassword",
}
user := &User{
    Username: userDTO.Username,
    Password: userDTO.Password,
}

Similarly, we can also convert User to UserDTO:

user := &User{
    ID: "1",
    Username: "testuser",
    Password: "testpassword",
}
userDTO := &UserDTO{
    Username: user.Username,
    Password: user.Password,
}

The above code demonstrates DTO conversion from UserDTO to User and from User to UserDTO.

4. Use reflection for DTO conversion

When the DTO has a large number of attributes, manually performing DTO conversion can become tedious. In this case, using reflection makes it easier to implement DTO conversion.

For example, we can use the following code to perform reflection conversion from UserDTO to User:

type UserDTO struct {
    ID string
    Username string
    Password string
}

func (u *UserDTO) ToEntity() (*User, error) {
    user := &User{}
    elem := reflect.ValueOf(user).Elem()

    for i := 0; i < elem.NumField(); i++ {
        field := elem.Type().Field(i)
        tag := field.Tag.Get("json")
        sourceField := reflect.ValueOf(u).Elem().FieldByName(tag)

        if !sourceField.IsValid() {
            continue
        }

        destField := elem.Field(i)

        if !destField.IsValid() {
            continue
        }

        if !destField.CanSet() {
            continue
        }

        destField.Set(sourceField)
    }

    return user, nil
}

The above code uses reflection to convert UserDTO to User. The code first creates an empty User object and then uses the reflect.ValueOf method to get the elem of the object. The code then loops through each field of the User object and checks if the field can be set. If the field can be set, the corresponding properties of the UserDTO object are copied to the corresponding properties of the User object.

In addition, you can also use a similar method to convert User to UserDTO. For example:

type User struct {
    ID string
    Username string
    Password string
}

func (u *User) ToDTO() (*UserDTO, error) {
    userDTO := &UserDTO{}
    elem := reflect.ValueOf(userDTO).Elem()

    for i := 0; i < elem.NumField(); i++ {
        field := elem.Type().Field(i)
        tag := field.Tag.Get("json")
        sourceField := reflect.ValueOf(u).Elem().FieldByName(field.Name)

        if !sourceField.IsValid() {
            continue
        }

        destField := elem.Field(i)

        if !destField.IsValid() {
            continue
        }

        if !destField.CanSet() {
            continue
        }

        destField.Set(sourceField)
    }

    return userDTO, nil
}

The above code uses a similar method to convert the User object to UserDTO.

5. Conclusion

This article introduces what DTO is and why DTO conversion is needed in the application. This article demonstrates how to define DTO in Go, and provides two ways to convert DTO into entity objects, manually and through reflection. DTO conversion is a problem often encountered in Go applications, using DTO can make the code more readable and maintainable.

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