（可选）将.Where（）应用于gorm.DB

I am new to Go and my pointer knowledge is rusty. I want to mutate an instance of the gorm.DB so that I can apply 0 or more Where clauses to it.

func () {
    db := gorm.Open(/* ... */)
    err := applyWhere(db, filters).Order("created_datetime desc").Find(&rMessages).Error
    // ...
}

func applyWhere(db *gorm.DB, filters Filters) *gorm.DB {
    if filters.MessageType != "" {
        db = db.Where(&message{MessageType: string(filters.MessageType)})
    }
    return db
}

This seems not to work. The db instance doesn't have the where applied.

* edit 3 *

This now works. Not sure what the problem was before. Please close / delete this question.

Read on how to do chaining with GORM properly here: Method Chaining tutorial. You take the *gorm.DB returned by one method and apply another method to it, that's it. You can also pass the *gorm.DB around, but be careful to only pass the pointer, not dereference it (otherwise you get the lock copy error as you found).

Orders are just another kind of query you can chain: http://gorm.io/docs/query.html#Order

For example:

var p Product
db.Order("Price").Where("Price > 1000").First(&p)

So your applyWhere should just return *gorm.DB which you can further query