ios - Swift - 函数在附加字典中的键值后仅返回 nil？

Question

Swift 新手。对类(class)有一定的了解。我有一个 getSomething() 函数，该函数应该返回从字典附加的键值数组(不是值本身，而是它们的键)。但是，我的函数只返回 nil

public class MyClass {
            private var somethingA : String
            private var somethingB : String
            private var somethingC : Int

            // A dictionary
            // For example, if I add a fruit, color and price
            // ["Apple":["red":5]]
            private var complexes:[String:[String:Int]] = [String:[String:Int]]();

            init() {
                 self.somethingA = "";
                 self.somethingB = "";
                 self.somethingC = 0;
                 self.complexes = [somethingA:[somethingB:somethingC]];

            }

            // Adds a string to the dict complexes
            // For example, ["Apple] = ["", 0]
            public func addSomething(somethingAA : String) {

                 self.somethingA = somethingAA;
                 self.complexes[somethingAA] = [self.somethingB : self.somethingC];
            }

            // Adds a whole entry to the dict complexes
            // For example, ["Apple"] = ["red": 5]
            public func addComplex(somethingAA:  String, complex:(somethingBB:  String,  somethingCC:  Int)) {

                self.somethingA = somethingAA
                self.somethingB = complex.somethingBB
                self.somethingC = complex.somethingCC

                complexes[somethingAA] = [complex.somethingBB: complex.somethingCC]
            }

            // My Problem:  only returns nil
            public func getSometing() -> [String]?{

                 var myArray:[String]? = nil;

                 let keys = Array(complexes.keys);

                 for key in keys { myArray?.append(key); } // This may be the line of code that isn't properly working

                 return myArray;
            }    
        }

我的测试文件:

 var sampleObject:MyClass;
 sampleObject = MyClass();

 sampleObject.addSomething(somethingAA:  "Apple");
 sampleObject.addSomething(somethingAA:  "Orange");

 print(sampleObject.getSomething());

我的 getSomething() 函数仅打印 nil ，这意味着它没有将正确的 keys 附加到 myArray

不太清楚为什么。由于这是我使用 Swift 的头几天，所以还没有真正使用或熟悉 nils，但我在 Java 和 C# 中使用过 nulls。 nils 等同于 nulls 吗？

我想要的正确输出应该返回如下:

["Apple", "Orange"] // not necessarily in order

Answer 1

您尚未初始化数组。所以事情应该是这样的:

public func getSometing() -> [String]?{
   var myArray = [String]();
   let keys = Array(complexes.keys);
   for key in keys { myArray?.append(key); } // This may be the line of code that isn't properly working
   return myArray;
   }