如何通过多个元素过滤数组并在Swift中找到总和？(How to filter the array by multiple element and find the sum in Swift?)

 我试图通过一些元素来过滤我的数组。 我想记录类型包含“收入”和$0.createdAt!等于一个日期，但$0.createdAt! 是一个日期类型，所以我不能使用.contain("") ，我可以使用什么？ 
 
recordFilter = record.filter { $0.recordtype!.contains("Income") /*|| $0.createdAt! = recordItem.createdAt!*/}
 
 recordFilter输出:(此结果不是由createdAt过滤） 
 
[<Record: 0x600000099fa0> (entity: Record; id: 0xd0000000003c0000 <x-coredata://913F25A5-B2C9-4646-9091-5EFE7F906908/Record/p15> ; data: {
    accountbook = "first book";
    amount = "\U00a59.99";
    assest = nil;
    category = "\U6295\U8d44";
    createdAt = "2017-11-16 16:00:00 +0000";
    date = nil;
    id = 15;
    recordtype = "\U6536\U5165";
    remark = "";
    toAccBook = nil;
}), <Record: 0x600000099ff0> (entity: Record; id: 0xd000000000400000 <x-coredata://913F25A5-B2C9-4646-9091-5EFE7F906908/Record/p16> ; data: {
    accountbook = "first book";
    amount = "\U00a56.58";
    assest = nil;
    category = "\U5de5\U8d44";
    createdAt = "2017-11-16 16:00:00 +0000";
    date = nil;
    id = 16;
    recordtype = "\U6536\U5165";
    remark = "";
    toAccBook = nil;
})]
 
 之后，我尝试获取数组中的所有数量字符串并对其进行求和。 但是当我使用这段代码的时候，我发现它全部是单独的字符串，我怎样才能将它分组到数组中并且对它进行求和或者有其他方法来做到这一点？ 
 
let sum = recordFilter.map({Int($0.amount!.dropFirst())})
//[nil, nil]

for i in 0..<recordFilter.count{
    if recordFilter[i].amount != nil{

        let amountList = recordFilter[i].amount!.dropFirst()
        print(amountList) // I found that it's separate string.
        //9.99
        //11.22
        // ...

        //let intArray = amountList.map { Int($0)!}
        //let sum = amountList.reduce(0, +)
        //print(sum)

    }
}

I'm trying to filter my array by some element. I want recordtype is contain "Income" and createdAt equal to a date but $0.createdAt! is an date type so I can't use .contain(""), what can I use?
 
recordFilter = record.filter { $0.recordtype!.contains("Income") /*|| $0.createdAt! = recordItem.createdAt!*/}
 
recordFilter output: (this result is not filter by createdAt yet)
 
[<Record: 0x600000099fa0> (entity: Record; id: 0xd0000000003c0000 <x-coredata://913F25A5-B2C9-4646-9091-5EFE7F906908/Record/p15> ; data: {
    accountbook = "first book";
    amount = "\U00a59.99";
    assest = nil;
    category = "\U6295\U8d44";
    createdAt = "2017-11-16 16:00:00 +0000";
    date = nil;
    id = 15;
    recordtype = "\U6536\U5165";
    remark = "";
    toAccBook = nil;
}), <Record: 0x600000099ff0> (entity: Record; id: 0xd000000000400000 <x-coredata://913F25A5-B2C9-4646-9091-5EFE7F906908/Record/p16> ; data: {
    accountbook = "first book";
    amount = "\U00a56.58";
    assest = nil;
    category = "\U5de5\U8d44";
    createdAt = "2017-11-16 16:00:00 +0000";
    date = nil;
    id = 16;
    recordtype = "\U6536\U5165";
    remark = "";
    toAccBook = nil;
})]
 
After that, I trying to get all the amount string in array and sum it. But I found that it's all separate string when I use this code, how can I group it in array and sum it or have any other way to do it?
 
let sum = recordFilter.map({Int($0.amount!.dropFirst())})
//[nil, nil]

for i in 0..<recordFilter.count{
    if recordFilter[i].amount != nil{

        let amountList = recordFilter[i].amount!.dropFirst()
        print(amountList) // I found that it's separate string.
        //9.99
        //11.22
        // ...

        //let intArray = amountList.map { Int($0)!}
        //let sum = amountList.reduce(0, +)
        //print(sum)

    }
}

原文：https://stackoverflow.com/questions/47343382