英文:
How to make Go append work inside a range loop
问题
我有一个函数，它从一个结构体中获取未知数量的输入：
func GetAllXXXByQueryFilters(ctx context.Context, filters ...XXXFilters) ([]XXX, error) {
var allKeys []*datastore.Key
var xxx []XXX
for _, filter := range filters {
query := datastore.NewQuery("XXX")
if filter.Foo != "" {
query = query.Filter("foo =", filter.Foo)
}
if filter.Bar != "" {
query = query.Filter("bar =", filter.Bar)
}
keys, err := models.DSClient().GetAll(ctx, query, &xxx)
if err != nil {
return nil, err
}
allKeys = append(allKeys, keys...) // 在这里解决问题
}
for i, key := range allKeys {
xxx[i].ID = key.ID
}
return xxx, nil
}
问题在于allKeys会覆盖之前的查询结果。我之前通过以下方式解决了这个问题：
keys1, err := models.DSClient().GetAll(ctx, query1, &xxx)
keys2, err := models.DSClient().GetAll(ctx, query2, &xxx)
keys = append(keys1, keys2...)
但是我希望GetAllXXXByQueryFilters函数更加复杂，避免重复的代码，现在我似乎无法找到如何在for _, filter := range filters循环中存储键并在之后将它们全部追加的方法。所以我希望也许有一种更聪明的方法来替代allKeys = append(keys)这一行，以避免覆盖之前的键。
英文:
I have this function which takes an unknown amount of input from a struct:
func GetAllXXXByQueryFilters(ctx context.Context, filters ...XXXFilters) ([]XXX, error) {
var allKeys []*datastore.Key
var xxx []XXX
for _, filter := range filters {
query := datastore.NewQuery("XXX")
if filter.Foo != "" {
query = query.Filter("foo =", filter.Foo)
}
if filter.Bar != "" {
query = query.Filter("bar =", filter.Bar)
}
keys, err := models.DSClient().GetAll(ctx, query, &xxx)
if err != nil {
return nil, err
}
allKeys = append(keys) // PROBLEM HERE
}
for i, key := range allKeys {
xxx[i].ID = key.ID
}
return xxx, nil
}
The problem is that allKeys will override previous query results. I have previously overcome the problem by doing:
keys1, err := models.DSClient().GetAll(ctx, query1, &xxx)
keys2, err := models.DSClient().GetAll(ctx, query2, &xxx)
keys = append(keys1, keys2...)
But I wanted my GetAllXXXByQueryFilters to be more sophisticated and avoid duplicated code, and now I can't seem to figure out how I can store the keys from the for _, filter := range filters loop and then append them all afterwards. So I was hoping that maybe there was a smarter way to do/replace the allKeys = append(keys) line so that it doesn't override previous keys?
答案1
得分: 1
将内容翻译为中文：
追加到切片的方法如下：
allKeys = append(allKeys, keys...)
append函数的第一个参数是切片，其余参数是要追加到切片的元素。append函数返回新的切片。
英文:
Append to the slice like this:
allKeys = append(allKeys, keys...)
The first argument to append is the slice. The remaining arguments are the elements to append to the slice. The append function returns the new slice.
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