真不是標(biāo)題黨勺像，除了正常的算數(shù)運(yùn)算，其他的千萬要繞著"+"運(yùn)算遠(yuǎn)一點(diǎn)啊错森。

這2天Xcode把我們團(tuán)隊(duì)坑瘸了吟宦，隨著代碼越來越多，這編譯速度就越來越慢涩维，越來越慢……今天我一個(gè)下午一邊敲一遍編譯殃姓，就編譯成功了一次，簡直是令人發(fā)指啊蜗侈！??

實(shí)在是不能忍了篷牌，滿世界找了找原因，在stackoverflow上找到這個(gè)編譯時(shí)間查看工具BuildTimeAnalyzer-for-Xcode踏幻，再回想起了一個(gè)零贊同的我以為是亂寫的回答(當(dāng)時(shí)覺得完全不可能才印象深刻)枷颊，逐漸開始找到了頭緒，項(xiàng)目編譯慢的主要原因居然真是因?yàn)樗f的"+"運(yùn)算導(dǎo)致的叫倍。我靠偷卧！

下面是BuildTimeAnalyzer運(yùn)行圖。每一行都是一個(gè)swift文件(或某個(gè)swift文件的一個(gè)closure)的編譯時(shí)間……項(xiàng)目里的這些文件大多有共同的特征：多個(gè)string類型的變量以+運(yùn)算相連吆倦。恩听诸，一個(gè)230行代碼的文件，也就編譯了4分鐘而已嘛蚕泽。

image.png

然后順藤摸瓜找到了這個(gè)討論http://stackoverflow.com/questions/29707622/bizarre-swift-compiler-error-expression-too-complex-on-a-string-concatenation晌梨，Honey的回答大致意思就是說swift3的 "+ " 運(yùn)算嚴(yán)重超載了，運(yùn)算時(shí)間會呈指數(shù)級的增長须妻？仔蝌？？；睦簟Ａ簿！

image.png

怎么不用+號绰更，大家應(yīng)該都知道吧瞧挤，let combinedString = "\(hello) \(world)"就好了。本文還沒結(jié)束儡湾，我發(fā)現(xiàn)stackoverflow上其他一些開發(fā)者的說法特恬，也一齊轉(zhuǎn)過來了。

比如說Stefan Nestorov說不能這樣使用??,會編譯慢：

let name = "\(someString ?? "")"

bibscy說Dictionary不能這樣寫

func toAnyObject() -> AnyObject {
  return
      ["BookingAmount":BookingAmount,
     "BookingNumber":BookingNumber,
     "PostCode":PostCode,
     "SelectedBathRow":SelectedBathRow,
     "SelectedBedRow":SelectedBedRow,
     "DateAndTime":DateAndTime,
     "TimeStampDateAndTime":TimeStampDateAndTime,
     "TimeStampBookingSavedInDB": TimeStampBookingSavedInDB,
     "FrequencyName":FrequencyName,
     "FrequecyAmount":FrequecyAmount,
     "insideCabinets": insideCabinets,
     "insideFridge": insideFridge,
     "insideOven": insideOven,
     "laundryWash": laundryWash,
     "interiorWindows": interiorWindows,
     "FullName":FullName,
     "SuppliesName":SuppliesName,
     "SuppliesAmount":SuppliesAmount,
     "FlatNumber":FlatNumber,
     "StreetAddress":StreetAddress,
     "PhoneNumber":PhoneNumber,
     "EmailAddress":EmailAddress] as AnyObject
}

要這樣寫：

func toAnyObject() -> AnyObject {

    var someDict = [String : AnyObject]()
    someDict["BookingAmount"] = self.BookingAmount as AnyObject?
    someDict["BookingNumber"] = self.BookingNumber as AnyObject?
    someDict["PostCode"] = self.PostCode as AnyObject?
    someDict["SelectedBathRow"] = self.SelectedBathRow as AnyObject?
    someDict["SelectedBedRow"] = self.SelectedBedRow as AnyObject?
    someDict["DateAndTime"] = self.DateAndTime as AnyObject?
    someDict["TimeStampDateAndTime"] = self.TimeStampDateAndTime as AnyObject?
    someDict["TimeStampBookingSavedInDB"] = self.TimeStampBookingSavedInDB as AnyObject?
    someDict["FrequencyName"] = self.FrequencyName as AnyObject?
    someDict["FrequecyAmount"] = self.FrequecyAmount as AnyObject?
    someDict["insideCabinets"] = self.insideCabinets as AnyObject?
    someDict["insideFridge"] = self.insideFridge as AnyObject?
    someDict["insideOven"] = self.insideOven  as AnyObject?
    someDict["laundryWash"] = self.laundryWash as AnyObject?
    someDict["interiorWindows"] = self.interiorWindows as AnyObject?
    someDict["FullName"] = self.FullName as AnyObject?
    someDict["SuppliesName"] = self.SuppliesName as AnyObject?
    someDict["SuppliesAmount"] = self.SuppliesAmount as AnyObject?
    someDict["FlatNumber"] = self.FlatNumber as AnyObject?
    someDict["StreetAddress"] = self.StreetAddress as AnyObject?
    someDict["PhoneNumber"] = self.PhoneNumber as AnyObject?
    someDict["EmailAddress"] = self.EmailAddress as AnyObject?

    return someDict as AnyObject
}

Ben Simon說Array不要這樣寫

let array = ["1", "2", "3", "4", "5", "6", "7", "8"]

而要寫成這樣：

let array: Array<String> = ["1", "2", "3", "4", "5", "6", "7", "8"]

Dylan Gattey說

let combinedArrays = array1 + array2

是不好的徐钠，要這樣

[array1, array2].joined()

image.png

還讓不讓人用swift開發(fā)了癌刽！

所以用Xcode8.3開發(fā)swift應(yīng)用的同學(xué)們，如果你發(fā)現(xiàn)你的編譯速度慢的令人發(fā)指尝丐，一定要記得你看過本文跋园荨！

Xcode8.3/Swift3簡直是謀財(cái)害命摊崭。10天一新版讼油，都發(fā)了3版了，還是這么爛澳佤ぁ矮台！