我有一个查询从服务器获取对象然后通过将“packName”与“className”匹配来减少对象的数量，这应该只给我“packName”的子项。
从这里我填充一个结构项数组并拉出数组的第一个索引的数据。
这很好，但我有点担心，如果孩子的数量增加，这可能会减慢处理速度。所以我想知道是否有办法只检索for循环的第一项，这是我所追求的，因为查询已按升序排序。
这是下面的功能代码。
class func createHistory(packName: String, completeBlock: ((Bool) -> Void)? = nil) {
struct initialDataStruct {
var packNameStruct : String
var packIdStruct : String
var partNameStruct : String
var partIdStruct : String
var partIndexStruct : Int
}
var initialDataArray = [initialDataStruct]()
let historyClass = PFObject(className: packName)
let query = PFQuery(className: "Part")
query.includeKey("fromPack")
query.order(byAscending: "partName")
query.fromLocalDatastore()
query.findObjectsInBackground { (objects, error) in
if error != nil {
print(error!)
}
else if let parts = objects {
for object in parts {
// if the fromPack column has data
if let fromPack = object.object(forKey: "fromPack") as? PFObject {
// create the class name from the pack name
if let className = (fromPack.object(forKey: "packName") as? String) {
// packName was sent from JVC
// this will limit array items to how ever many children packName has
if packName == className {
// because its sorted could probably just get the first item here
let packName = fromPack.object(forKey: "packName") as! String
let packId = fromPack.objectId as String!
let partName = object.object(forKey: "partName") as! String
let partId = object.objectId as String!
let partIndex = 0
initialDataArray.append(initialDataStruct(packNameStruct: packName,
packIdStruct: packId!,
partNameStruct: partName,
partIdStruct: partId!,
partIndexStruct: partIndex))
}
}
}
} // for
historyClass.add(initialDataArray[0].packNameStruct, forKey: "packName")
historyClass.add(initialDataArray[0].partIdStruct, forKey: "packId")
historyClass.add(initialDataArray[0].partNameStruct, forKey: "partName")
historyClass.add(initialDataArray[0].partIndexStruct, forKey: "partIndex")
print(historyClass)
PFObject.pinAll(inBackground: [historyClass])
}
} // query
}