Swift：unwrapping导致swift编译缓慢 [英] Swift: unwrapping cause swift compile slowly

问题描述

在 func tableView（tableView：UITableView！，cellForRowAtIndexPath indexPath：NSIndexPath！） - > UITableViewCell！{

这行代码使swift编译速度极慢：

this line of code makes swift compile extremely slow:

cell!.detailTextLabel.text = child.year! + " " + child.make! + " " + child.model!

如果我有这行代码，我需要1分44秒才能构建项目。并且有99％的时间它坚持编译Swift源文件。
如果我将此行更改为

It takes me 1 min and 44 secs to build the project if I have this line of code. And 99% of the time it stuck at "Compiling Swift source files". If I change this line to

cell!.detailTextLabel.text = " "//child.year! + " " + child.make! + " " + child.model!

构建项目只需要5或6秒。
我想知道为什么这行代码会导致如此多的时间编译。

It only take me 5 or 6 sec to build the project. I would like to know why this line of code will cause so much time compiling.

在我的Child模型中，它们被声明为：

In my Child model, they are declared as :

var name:String?
var year:String?
var make:String?
var model:String?

和init：

init(name:String!, ... ,year:String!, make:String!, model:String!, ...){
        self.name = name
       ...
        self.year = year
        self.make = make
        self.model = model
}

我构建一个孩子的部分：

The part I construct a child:

Child(name:cName,...,year:cYear,make:cMake, model:cModel,...)

推荐答案

是的，我在这个缓慢的编译问题上提交了一个错误报告（17585851），你应该这样做;苹果发送的用例越明确越好。我的慢代码是这种形式的几次出现：

Yes, I filed a bug report (17585851) on this slow compilation issue, and you should do the same; the more clear use cases Apple is sent, the better. My slow code was several occurrences of this form:

let title = obj.valueForProperty(MPMediaItemPropertyTitle) as? String
self.titles += title ? title! : ""

（正如您所看到的，正在进行零测试/解包）。对我来说，通过以不同的方式做同样的事情来解决问题并不困难，但你也应该这样做。但首先提交bug报告！

(which, as you can see, is doing nil testing / unwrapping). It was cumbersome but not difficult for me to work around the problem by doing the same thing in a different way, and you should do likewise. But file that bug report first!

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