从swift3开始我无法可靠地检测到nil / NSNull。在此代码段中，我得到的nil值不是Optional(_SwiftValue)，而是func testVotingMachine() {
let vote: String? = nil // Can be a string or nil
//let vote: String? = "president" // Can be a string or nil
var dict = [String: AnyObject?]()
dict["vote"] = vote as AnyObject?
let obj: AnyObject? = dict as AnyObject?
guard let dict2 = obj as? Dictionary<String, AnyObject?> else {
fatalError()
}
let value = dict2["vote"] as AnyObject?
let didVote = notNil(objectOrNil: value)
XCTAssertFalse(didVote) // BOOM! notNil() fails to detect nil
}
func notNil(objectOrNil: AnyObject?) -> Bool {
guard let object: AnyObject = objectOrNil else {
return false
}
if object is NSNull {
return false
}
//if object.classForCoder == NSNull.classForCoder() {
// return false
//}
// TODO: how to check for? Optional(_SwiftValue)
print("class for coder: \(object.classForCoder)")
return true
}
，我不知道如何检测。
我没有运气就试过checking classForCoder。
其他地方有talk about id-as-Any causing this kind of problem
JSONSerialization.data()我需要在将数据传递给Optional(_SwiftValue)之前对其进行清理。因此，我需要检测//method for runtime testing for getNthPopular()
// Average time for getNthPopular();
Trends tr = new StudentTrends();
//...more code
int n = tr.numEntries(); //number of pairs
startTime = System.nanoTime();
for (int i = 0; i < n; i++)
//get the Nth popular string term in the textfile
tr.getNthPopular(i);
endTime = System.nanoTime();
double test3 = (double)((endTime - startTime)/1000000.0)/(double)n;
System.out.println("Test 3: " + test3 + " milliseconds /getNthPopular");
//................runtime testing method ends...................
答案 0 :(得分：2)
Rewrite是String?的简写。当它为零时，它实际上表示为Optional<String>，其符合条件为非零Optional<String>.none，因此您的测试不起作用。
你可以这样解决：
AnyObject