英文:
Go adding items to array recursively not working
问题
我一直在进行一些 Golang 编程，通常都很有趣。现在我有这段代码，需要将其从 C# 移植到 Go，但它就是无法正常工作。
这个代码的想法是从数据库中填充一个员工树，但是每次调用时内部的切片都没有被填充。
最好在这里写下代码：
func (db *DalBase) TitleAllChildren(tx *gorp.Transaction) (items []Title, err error) {var dbChildren []entities.Title_, err = tx.Select(&dbChildren, "select * from title where idparent is null order by name")if err != nil {return}items = make([]Title, 0)for i := range dbChildren {currItem := &dbChildren[i]item := &Title{Id: currItem.Id, Name: currItem.Name}err = db.TitleChildrenRecursive(tx, item)if err != nil {return}items = append(items, *item)}return}func (db *DalBase) TitleChildrenRecursive(tx *gorp.Transaction, u *Title) (err error) {var dbChildren []entities.Title_, err = tx.Select(&dbChildren, "select * from title where idparent = $1 order by name", u.Id)if err != nil {return}if len(dbChildren) != 0 {u.Items = make([]Title, 0)for i := range dbChildren {currItem := &dbChildren[i]item := &Title{Id: currItem.Id, Name: currItem.Name}err = db.TitleChildrenRecursive(tx, item)if err != nil {return}u.Items = append(item.Items, *item)}}return}
我已经在每次递归调用时记录了值，并且它们在函数内部被填充，但是当它向上冒泡到父级时，切片为空。
我不想使用切片的指针，有可能实现吗？
编辑：这是我尝试填充的结构体：
type Title struct {Id string `json:"id"`Name string `json:"name"`Items []Title `json:"items"`}
英文:
I have been doing some golang programming and usually has been lot of fun. Now I have this code I need to port from C# to go and it is just not working.
The idea is to fill a tree of employees from database but inner slices are not being filled up on each call.
Better to write the code here
func (db *DalBase) TitleAllChildren(tx *gorp.Transaction) (items []Title, err error) {var dbChildren []entities.Title_, err = tx.Select(&dbChildren, "select * from title where idparent is null order by name")if err != nil {return}items = make([]Title, 0)for i := range dbChildren {currItem := &dbChildren[i]item := &Title{Id: currItem.Id, Name: currItem.Name}err = db.TitleChildrenRecursive(tx, item)if err != nil {return}items = append(items, *item)}return}func (db *DalBase) TitleChildrenRecursive(tx *gorp.Transaction, u *Title) (err error) {var dbChildren []entities.Title_, err = tx.Select(&dbChildren, "select * from title where idparent = $1 order by name", u.Id)if err != nil {return}if len(dbChildren) != 0 {u.Items = make([]Title, 0)for i := range dbChildren {currItem := &dbChildren[i]item := &Title{Id: currItem.Id, Name: currItem.Name}err = db.TitleChildrenRecursive(tx, item)if err != nil {return}u.Items = append(item.Items, *item)}}return}
I have logged the values on each recursive call and they are being filled inside the function, but when it bubbles up to the parent, slices are empty.
I wouldn't like to use pointers to slices, is it possible to implement?
Edit: here is the struct I am trying to fill
type Title struct {Id string `json:"id"`Name string `json:"name"`Items []Title `json:"items"`}
答案1
得分: 3
你不需要一个指向切片的指针，只要你传递一个指向包含切片的结构体的指针。
每次调用TitleChildrenRecursive时，在追加任何内容之前，你都会用一个新的切片替换原来的切片：
u.Items = make([]Title, 0)
没有必要使用make创建一个新的切片，因为append函数可以正确地处理空切片。
你还应该将[]Title改为[]*Title，这样，如果在将子项添加到切片后进行任何append操作，整个树都会反映出来。
英文:
You won't need a pointer to a slice, as long you are passing around a pointer to the struct which contains your slice.
Each time you call TitleChildrenRecursive, you're replacing your slice with a new one before anything is appended:
u.Items = make([]Title, 0)
There's no need to make a new slice, since append works correctly with a nil slice.
You should also change []Title to []*Title, so that if any append operations happen to children items after they are added to the slice, it's reflected throughout the tree.
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