gocraft / dbr：如何加入多个条件？

Question

I develop web application with golang. I use the library gocraft/dbr as O/R Mapper.

I have two tables: image and entry. I join their tables and I want to get image_url.

type Image struct {
    ImageUrl   dbr.NullString `db:"image_url"`
}

type Entry struct {
    CompanyImageID   dbr.NullInt64  `db:"company_image_id"`
    CompanyImage Image
    EyecatchIamgeID dbr.NullInt64  `db:"eyecatch_image_id"`
    EyecatchImage Image
}

Then I tried below:

var entry Entry
sess.Select("*").From("entry").
    LeftJoin(dbr.I("image").As("eyecatch_image"), "entry.eyecatch_image_id = eyecatch_image.id").
    LeftJoin(dbr.I("image").As("company_image"), "entry.company_image_id = company_image.id").
    Load(&entry)
log.Println("company:", entry.CompanyImage)
log.Println("eyecatch:", entry.EyecatchImage)   

result:

company: {{{https://company_image_url.png true}}}
eyecatch: {{{ false}}}

I expect below, but it did not become as expected.

company: {{{https://company_image_url.png true}}}
eyecatch: {{{{http://eyecatch_image_url.png true}}}

When I tried to change join condition like below:

sess.Select("*").From("entry").
    LeftJoin(dbr.I("image").As("eyecatch_image"), "entry.eyecatch_image_id = eyecatch_image.id")
    Load(&entry)

result:

company: {{{http://eyecatch_image_url.png true}}}
eyecatch: {{{ false}} {{ false}}}}

I don't know how to use join with multiple conditions.

Thank you.

Answer 1

The documentation is really poor - it seems they gave up on the idea of publishing the library. There is an open pull request that provides a little better documentation.. Here the author describes that you can create a multiple condition like this:

cond:= dbr.And(
  dbr.Or(
    dbr.Gt("created_at", "2015-09-10"),
    dbr.Lte("created_at", "2015-09-11"),
  ),
  dbr.Eq("title", "hello world"),
)

Then use the condition in any statement:

sess.Select("*").From("entry").
    LeftJoin(dbr.I("image").As("eyecatch_image"), cond)
    Load(&entry)