通过比较两个数组来找到对象

Question

我有两个数组，它们有相同的模型。

我试图找到它具有相同ID的对象。我试过这种方法，我可以找到它，但我怎么可以让它没有循环？

for item in userList { 

     let userSelection = user.list.first(where: {$0.id == item.id}) 
     item.approved = userSelection.approved 

     print(userSelection) 
    } 

Answer 1

如果你不关心性能，你可以使用set.intersection：

let set1:Set<UserType> = Set(userList) 
let set2:Set<UserType> = Set(user.list) 
let commonItems = set1.intersection(set2)// Intersection of two sets 

Answer 2

尝试是这样的

let userSelection = user.list.filter({userList.map({$0.id}).contains({$0.id})}) 

说明：

//get all the ids from one list 
let ids = userList.map({$0.id}) 

//filter the second list by including all the users whose id is in the first list 
let userSelection = user.list.filter({ids.contains({$0.id})}) 

Answer 3

即使如果y我们的模型不是Hashable，你可以使用集合来执行验证：

if Set(userList.map{$0.id}).subtracting(user.list.map{$0.id}).count == 0 
{ 
    // all entries in userList exist in user.list 
} 
else 
{ 
    // at least one entry of userList is not in user.list 
}