android APK在一个APK中？(android APK within an APK?)

 一个CLLocation! 变量是可选的，但它只是一个隐式解包的变量。 正如The Swift Programming Language：The Basics所说： 
 
 
 
 [Optionals]表示允许常量或变量具有“无值”。 可以使用if语句检查Optionals，以查看是否存在值，并且可以使用可选绑定有条件地解包，以访问可选的值（如果存在）。 
 
 
 有时从程序的结构中可以清楚地看出，在首次设置该值之后，可选项将始终具有值。 在这些情况下，每次访问时都不需要检查和解包可选的值，因为可以安全地假设它始终具有值。 
 
 
 这些类型的选项被定义为隐式解包的选项。 您可以通过在要使其成为可选类型之后放置感叹号（ String! ）而不是问号（ String? ）来编写隐式解包的可选项。 
 
 
 因此， location是一个可选项，但您不必在每次使用它时都显式解包它，因为它是一个隐式解包的。 

A CLLocation! variable is an optional, but it is just a implicitly unwrapped one. As The Swift Programming Language: The Basics says:
 
 
 
[Optionals] indicate that a constant or variable is allowed to have “no value”. Optionals can be checked with an if statement to see if a value exists, and can be conditionally unwrapped with optional binding to access the optional’s value if it does exist.
 
 
Sometimes it is clear from a program’s structure that an optional will always have a value, after that value is first set. In these cases, it is useful to remove the need to check and unwrap the optional’s value every time it is accessed, because it can be safely assumed to have a value all of the time.
 
 
These kinds of optionals are defined as implicitly unwrapped optionals. You write an implicitly unwrapped optional by placing an exclamation mark (String!) rather than a question mark (String?) after the type that you want to make optional.
 
 
So, location is an optional, but you don't have to explicitly unwrap it every time you use it because it is an implicitly unwrapped for you.