\u5b66\u4e60Swift\u65f6\uff0c\u7edd\u5927\u591a\u6570\u521d\u5b66\u8005\u90fd\u4f1a\u88abSwift\u4e2d\u7684Optional\u8fd9\u4e2a\u7c7b\u578b\u6240\u56f0\u6270\uff0c\u6bd4\u5982\u201c\u95ee\u53f7\u662f\u4ec0\u4e48\uff1f\u201d\u3001\u201c\u53f9\u53f7\u662f\u4ec0\u4e48\uff1f\u201d\u3001\u201c\u4e3a\u4ec0\u4e48\u8fd9\u91cc\u8981\u52a0\u95ee\u53f7\/\u53f9\u53f7\uff1f\u201d\u7b49\u7b49\uff0c\u8fd9\u7bc7\u6587\u7ae0\u5c06\u4f1a\u7ed3\u5408\u672c\u4eba\u7684\u4e00\u4e9b\u7ecf\u9a8c\u6765\u8c08\u8c08Swift\u7684Optional\u7c7b\u578b\u3002<\/p>\n
Swift\u662f\u4e00\u95e8\u9759\u6001\u8bed\u8a00\uff0c\u5728Swift\u4e2d\uff0c\u6240\u6709\u7684\u53d8\u91cf\u5e38\u91cf\u90fd\u9700\u8981\u5728\u7f16\u8bd1\u671f\u95f4\u786e\u5b9a\u7c7b\u578b\uff0c\u5728\u786e\u5b9a\u7c7b\u578b\u4e4b\u540e\uff0c\u7f16\u8bd1\u5668\u5c31\u53ef\u4ee5\u68c0\u67e5\u4ee3\u7801\u4e2d\u7684\u4e00\u4e9b\u9519\u8bef\uff0c\u6bd4\u5982\u6211\u4eec\u5728\u4ee3\u7801\u4e2d\u5c06\u4e00\u4e2aString\u7c7b\u578b\u7684\u503c\u8d4b\u7ed9\u4e00\u4e2aUIView\u7c7b\u578b\u7684\u53d8\u91cf\u65f6\uff0c\u7f16\u8bd1\u5668\u4f1a\u76f4\u63a5\u62a5\u9519\u3002<\/p>\n
var view: UIView = UIView()\r\nview = \"ABC\" \/\/ \u7f16\u8bd1\u5931\u8d25<\/pre>\n\u800cObjective-C\u662f\u4e00\u95e8\u52a8\u6001\u8bed\u8a00\uff0c\u8fd9\u4e2a\u64cd\u4f5c\u5728\u4e2d\u662f\u5141\u8bb8\u7684\u3002<\/p>\n
UIView *view = @\"ABC\"; \/\/ \u7f16\u8bd1\u548c\u8fd0\u884c\u90fd\u4e0d\u4f1a\u62a5\u9519\uff0c\u4f46\u5728\u8c03\u7528UIView\u7684\u5c5e\u6027\u6216\u65b9\u6cd5\u5219\u4f1acrash<\/pre>\n\u9759\u6001\u8bed\u8a00\u4f1a\u5728\u7f16\u8bd1\u671f\u95f4\u68c0\u67e5\u7c7b\u578b\u7684\u5408\u6cd5\u6027\uff0c\u4f7f\u7528\u9759\u6001\u8bed\u8a00\u6211\u4eec\u53ef\u4ee5\u4f9d\u8d56\u7f16\u8bd1\u5668\u6765\u68c0\u67e5\u51fa\u4e00\u4e9b\u4e0d\u7b26\u5408\u9884\u671f\u7684\u95ee\u9898\uff0c\u5728\u8fd0\u884c\u65f6A\u7c7b\u578b\u5c31\u662fA\u7c7b\u578b\uff0c\u4e0d\u4f1a\u51fa\u73b0\u725b\u5934\u4e0d\u5bf9\u9a6c\u5634\u7684\u9519\u8bef\u3002<\/p>\n
Optional\u7684\u672c\u8d28<\/h2>\n
\u90a3\u4e48\u5728Swift\u4e2d\uff0cnil\u7b97\u662f\u4ec0\u4e48\uff1fnil\u65e2\u4e0d\u662fString\u7c7b\u578b\u4e5f\u4e0d\u662fUIView\u7c7b\u578b\uff0c\u6211\u4eec\u65e0\u6cd5\u4fdd\u8bc1\u6240\u6709\u7684\u53d8\u91cf\u90fd\u5fc5\u5b9a\u4f1a\u6709\u503c\uff0c\u5f00\u53d1\u7684\u65f6\u5019\u4e0d\u53ef\u907f\u514d\u5730\u9700\u8981\u4f7f\u7528\u5230nil\u8981\u600e\u4e48\u529e\uff1fSwift\u7ed9\u51fa\u4e86\u8fd9\u6837\u4e00\u4e2a\u89e3\u51b3\u65b9\u6848\uff0c\u90a3\u5c31\u662fOptional\u7c7b\u578b\uff0c\u6211\u4eec\u5148\u6765\u770b\u770bOptional\u7684\u672c\u8d28\u662f\u4ec0\u4e48\uff0c\u4e0b\u9762\u662fOptional\u7c7b\u578b\u7684\u58f0\u660e\uff08\u5728Xcode\u4e2d\u6253\u51faOptional\u518d\u6309\u4f4fcommand\u70b9\u51fb\u5373\u53ef\u67e5\u770b\uff09<\/p>\n
public enum Optional<Wrapped> {\r\n\u00a0 \u00a0 \/\/\/ The absence of a value.\r\n\u00a0 \u00a0 \/\/\/\r\n\u00a0 \u00a0 \/\/\/ In code, the absence of a value is typically written using the `nil`\r\n\u00a0 \u00a0 \/\/\/ literal rather than the explicit `.none` enumeration case.\r\n\u00a0 \u00a0 case none\r\n\u00a0 \u00a0 \/\/\/ The presence of a value, stored as `Wrapped`.\r\n\u00a0 \u00a0 case some(Wrapped)\r\n}<\/pre>\n\u53ef\u4ee5\u770b\u5230\uff0cOptional\u662f\u5e26\u8303\u578b\u7684\u679a\u4e3e\u7c7b\u578b\uff0c\u8be5\u679a\u4e3e\u7c7b\u578b\u6709\u4e24\u79cd\u503c\u5206\u522b\u662fnone\u548csome\uff0csome\u7c7b\u578b\u8fd8\u5e26\u4e86\u4e00\u4e2a\u53c2\u6570\uff0c\u4ece\u6ce8\u91ca\u91cc\u6211\u4eec\u53ef\u4ee5\u770b\u5230\uff0cnil\u5176\u5b9e\u5c31\u662fOptional\u679a\u4e3e\u4e2d\u7684none\u8fd9\u4e2a\u503c\uff0c\u90a3\u4e48\u5230\u8fd9\u91cc\u8981\u7406\u89e3l\u5c31\u5f88\u7b80\u5355\u4e86\uff0c\u5c31\u50cf\u662f\u4e00\u4e2a\u7528\u4e00\u4e2a\u7bb1\u5b50\u6765\u5c06\u5185\u5bb9\u5b58\u653e\u8d77\u6765\uff0c\u7bb1\u5b50\u91cc\u53ef\u80fd\u653e\u4e86\u4e1c\u897f\uff08some\uff09\uff0c\u4e5f\u53ef\u80fd\u4ec0\u4e48\u4e5f\u6ca1\u6709\uff08none\uff09\uff0c\u5e76\u4e14Swift\u8fd8\u63d0\u4f9b\u4e86\u4e00\u4e9b\u8bed\u6cd5\u7cd6\u6765\u4f7f\u5f97Optional\u4f7f\u7528\u8d77\u6765\u66f4\u52a0\u65b9\u4fbf\uff08\u6bd4\u5982`XXX?`\u58f0\u660e`Optional<XXX>`\u3001\u53cc\u95ee\u53f7`??`\u63d0\u4f9b\u9ed8\u8ba4\u503c\u7b49\uff09\u3002<\/p>\n
Optional\u7c7b\u578b\u89e3\u5305<\/h2>\n
\u4e86\u89e3\u4e86Optional\u7684\u672c\u8d28\u540e\u53ef\u77e5`String?`\u548c`String`\u5e76\u4e0d\u662f\u540c\u4e00\u4e2a\u7c7b\u578b\uff0c\u524d\u8005\u5b9e\u8d28\u4e0a\u662f`Optional<String>`\u800c\u540e\u8005\u662f\u5b57\u7b26\u4e32\u7c7b\u578b`String`\uff0c\u5f53\u4e00\u4e2a\u65b9\u6cd5\u9700\u8981\u7684\u53c2\u6570\u662f`String`\u7c7b\u578b\u65f6\u4f20\u5165\u4e00\u4e2a`String?`\u7684\u8bdd\u4f1a\u56e0\u4e3a\u7c7b\u578b\u4e0d\u5339\u914d\u800c\u5bfc\u81f4\u7f16\u8bd1\u5668\u62a5\u9519\u3002<\/p>\n
\u90a3\u6211\u4eec\u5728\u5f00\u53d1\u8fc7\u7a0b\u4e2d\u8981\u5982\u4f55\u53bb\u901a\u8fc7\u4e00\u4e2aOptional\u7c7b\u578b\u7684\u503c\u53bb\u53d6\u51fa\u5b9e\u9645\u7c7b\u578b\u7684\u503c\u5462\uff1f\u65e2\u7136Optional\u662f\u4e00\u4e2a\u679a\u4e3e\u7c7b\u578b\uff0c\u90a3\u4e48\u6211\u4eec\u5c31\u53ef\u4ee5\u4f7f\u7528`switch`\u8bed\u53e5\u6765\u8fdb\u884c\u4e00\u4e9b\u5224\u65ad\u3002<\/p>\n
let value: String? = \"abc\"\r\nswitch value {\r\n\u00a0 case .none: break\r\n\u00a0 case .some(let text): print(text.count) \/\/ \u6b64\u5904text\u5df2\u7ecf\u662fString\u7c7b\u578b\r\n}<\/pre>\n\u5f00\u4e2a\u73a9\u7b11\uff0c\u5176\u5b9eSwift\u6709\u63d0\u4f9b\u4e00\u4e9b\u5f88\u65b9\u4fbf\u7684\u4e1c\u897f\u6765\u4ee3\u66ff\u8fd9\u4e2a`switch`\u7684\u5199\u6cd5\uff0c\u5728\u4ecb\u7ecd\u8fd9\u4e9b\u4e4b\u524d\uff0c\u8fd9\u91cc\u5148\u5b9a\u4e49\u4e00\u4e2a\u65b9\u6cd5\u4ee5\u4fbf\u4e4b\u540e\u4f7f\u7528\u548c\u8bb2\u89e3\u3002<\/p>\n
func printCount(of str: String) {\r\n\r\n\u00a0 print(str.count)\r\n\r\n}<\/pre>\n\u4f7f\u7528 if<\/b> let<\/b> \u6216 guard<\/b> let<\/b><\/h3>\n
Swift\u63d0\u4f9b\u4e86\u4e00\u4e9b\u65b9\u6cd5\u8ba9\u5f00\u53d1\u8005\u53ef\u4ee5\u6709\u6761\u4ef6\u5730\u89e3\u5f00\u4e00\u4e2aOptional\u5f97\u5230\u4e00\u4e2a\u65b0\u7684\u53d8\u91cf\uff0c\u6bd4\u8f83\u5e38\u89c1\u7684\u5c31\u662f`if<\/b> let<\/b>`\u548c`guard<\/b> let<\/b>`\u8bed\u53e5\u4e86\uff0c\u4e0a\u6587\u4e2d\u63d0\u5230\u7684`switch<\/b>`\u4e5f\u662f\u6709\u6761\u4ef6\u89e3\u5305\u7684\u4e00\u79cd\uff0c\u4f46\u5b9e\u9645\u5f00\u53d1\u4e2d\u4e0d\u5e38\u4f7f\u7528\u3002<\/p>\n
func testIfLet(text: String?) {\r\n\u00a0 \/\/ if let\u7684\u7528\u6cd5\r\n\u00a0 if let text = text {\r\n\u00a0 \u00a0 \/\/ \u82e5text\u4e0d\u4e3anil\u5219\u62c6\u5305\u6210\u529f\uff0c\u6761\u4ef6\u6210\u7acb\u6267\u884cif\u5185\u7684\u8bed\u53e5\r\n\u00a0 \u00a0 printCount(of: text)\r\n\u00a0 } else {\r\n\u00a0 \u00a0 \/\/ \u82e5text\u4e3anil\u5219\u6267\u884celse\u5185\u7684\u8bed\u53e5\r\n\u00a0 \u00a0 print(\"text is nil\")\r\n\u00a0 }\r\n}\r\n\r\nfunc testGuardLet(text: String?) {\r\n\u00a0 \/\/ guard let\u7684\u7528\u6cd5\r\n\u00a0 guard let text = text else {\r\n\u00a0 \u00a0 \/\/ \u82e5text\u4e3anil\u5219\u89e3\u5305\u5931\u8d25\u6267\u884celse\u5185\u7684\u8bed\u53e5\u5e76return\r\n\u00a0 \u00a0 print(\"text is nil\")\r\n\u00a0 \u00a0 return\r\n\u00a0 }\r\n\u00a0 printCount(of: text)\r\n}<\/pre>\n`if<\/b> let<\/b>`\u548c`guard<\/b> let<\/b>`\u5728\u89e3\u5305\u7684\u540c\u65f6\u8fd8\u53ef\u4ee5\u5224\u65ad\u8fd9\u4e2aOptional\u503c\u662f\u5426\u4e3anil\uff0c\u81f3\u4e8e\u5728\u5f00\u53d1\u4e2d\u9700\u8981\u4f7f\u7528`if<\/b> let<\/b>`\u8fd8\u662f`guard<\/b> let<\/b>`\u5c31\u89c1\u4ec1\u89c1\u667a\u4e86\uff0c\u4f7f\u7528`if<\/b> let<\/b>`\u5728\u89e3\u5305\u5931\u8d25\u540e\u4e5f\u53ef\u4ee5\u7ee7\u7eed\u6267\u884c\u5269\u4e0b\u7684\u4ee3\u7801\uff0c\u4f46`if<\/b> let<\/b>`\u4f7f\u7528\u8fc7\u591a\u53ef\u80fd\u4f1a\u51fa\u73b0if\u5d4c\u5957\u5730\u72f1\uff0c\u800c`guard<\/b>`\u867d\u7136\u53ef\u4ee5\u51cf\u5c11\u5d4c\u5957\u5c42\u6570\uff0c\u4f46\u662f`guard<\/b>`\u4e0d\u6210\u7acb\u65f6\u5fc5\u987b\u8981\u6267\u884c\u9000\u51fa\u5f53\u524d\u6d41\u7a0b\u7684\u8bed\u53e5\uff08return\u6216throw\u7b49\uff0c\u5982\u679c\u5728\u5faa\u73af\u4e2d\u8fd8\u53ef\u4ee5\u4f7f\u7528break\u548ccontinue\uff09\u3002<\/p>\n
\u5f3a\u5236\u89e3\u5305<\/h3>\n
\u9664\u4e86`if<\/b> let<\/b>`\u548c`guard<\/b> let<\/b>`\uff0cSwift\u8fd8\u63d0\u4f9b\u4e86\u5f3a\u5236\u89e3\u5305\u7684\u65b9\u6cd5\uff0c\u4e5f\u5c31\u662f\u6587\u7ae0\u7b2c\u4e00\u6bb5\u4e2d\u63d0\u5230\u7684\u53f9\u53f7\uff0c\u4f7f\u7528\u53f9\u53f7\u53ef\u4ee5\u76f4\u63a5\u89e3\u5305\u5f97\u5230\u4e00\u4e2a\u975eOptional\u7684\u5bf9\u8c61\u3002<\/p>\n
func testForceUnwrap(text: String?) {\r\n\u00a0 let abc = text! \/\/ \u8fd9\u91cc\u4f7f\u7528\u4e86\u53f9\u53f7\u8fdb\u884c\u5f3a\u5236\u89e3\u5305\uff0c\u56e0\u6b64abc\u7684\u7c7b\u578b\u4e3aString\u800c\u975eOptional\r\n\u00a0 printCount(of: text)\r\n}<\/pre>\n\u5f3a\u5236\u89e3\u5305\u5199\u8d77\u6765\u662f\u5f88\u65b9\u4fbf\uff0c\u4f46\u662f\u5f00\u53d1\u4e2d\u8981\u8c28\u614e\u4f7f\u7528\uff0c\u56e0\u4e3a\u5f53text\u4e3anil\u7684\u65f6\u5019\uff0c\u89e3\u5305\u5931\u8d25\u4f1a\u5bfc\u81f4\u5e94\u7528crash\uff0cSwift\u7684\u6587\u6863\u5bf9\u4e8e\u5f3a\u5236\u89e3\u5305\u7684\u63cf\u8ff0\u6700\u540e\u4e00\u53e5\u6709\u8bf4\u660e\u201c\u5bf9\u4e00\u4e2anil\u8fdb\u884c\u5f3a\u5236\u89e3\u5305\u4f1a\u53d1\u751f\u8fd0\u884c\u65f6\u9519\u8bef\u201d\uff0c\u56e0\u6b64\u5728\u5f00\u53d1\u5f53\u4e2d\uff0c\u9664\u975e\u80fd\u786e\u8ba4\u67d0\u4e2aOptional\u503c\u5728\u4f7f\u7528\u65f6\u7edd\u5bf9\u4e0d\u4f1a\u662fnil\uff0c\u5426\u5219\u8bf7\u4e0d\u8981\u4f7f\u7528\u53f9\u53f7\u8fdb\u884c\u5f3a\u5236\u89e3\u5305\u3002<\/p>\n
\u63d0\u4f9b\u9ed8\u8ba4\u503c<\/h3>\n
\u9664\u4e86\u901a\u8fc7\u4ee5\u4e0a\u65b9\u5f0f\u8fdb\u884c\u89e3\u5305\u4ee5\u5916\uff0cSwift\u8fd8\u63d0\u4f9b\u4e86`??`\u8fd0\u7b97\u7b26\u7528\u4e8e\u89e3\u5305\u5e76\u63d0\u4f9b\u9ed8\u8ba4\u503c\u3002<\/p>\n
func testDefaultValue(text: String?) {\r\n\u00a0 let abc = text ?? \"\" \/\/ \u82e5text\u4e0d\u4e3anil\u5219\u89e3\u5305\uff0c\u82e5\u4e3anil\u5219\u4f7f\u7528\u7a7a\u5b57\u7b26\u4e32\"\"\u4f5c\u4e3atext\u7684\u503c\r\n\u00a0 printCount(of: abc)\r\n}<\/pre>\n\u67d0\u4e9b\u65f6\u5019\u6211\u4eec\u5e76\u4e0d\u5173\u5fc3\u67d0\u4e2a\u53d8\u91cf\u662f\u5426\u4e3anil\uff0c\u6211\u4eec\u53ea\u5e0c\u671b\u4ee3\u7801\u80fd\u4e0d\u51fa\u95ee\u9898\u5730\u6267\u884c\u4e0b\u53bb\uff0c\u6bd4\u5982\u4e0a\u9762\u7684\u4ee3\u7801\uff0c\u5f53text\u4e3anil\u7684\u65f6\u5019\u8c03\u7528printCount\u65f6\u5728\u63a7\u5236\u53f0\u4e2d\u6253\u53700\u4e5f\u662f\u53ef\u4ee5\u63a5\u53d7\u7684\u7ed3\u679c\uff0c\u8fd9\u65f6\u5019\u4f7f\u7528`??`\u63d0\u4f9b\u9ed8\u8ba4\u503c\u8981\u6bd4`if<\/b> let<\/b>`\u6216`guard<\/b> let<\/b>`\u4ee5\u53ca\u5f3a\u5236\u89e3\u5305\u8981\u66f4\u52a0\u5408\u9002\u3002<\/p>\n
Optional Chaining<\/h2>\n
\u6709\u7684\u8bfb\u8005\u8bfb\u5230\u8fd9\u91cc\u7684\u65f6\u5019\u53ef\u80fd\u5c31\u60f3\u95ee\u4e86\uff0c\u201c\u524d\u9762\u89e3\u91ca\u4e86\u53f9\u53f7\u7684\u4f5c\u7528\uff0c\u90a3\u95ee\u53f7\u5462\uff1f\u201d\uff0c\u4e0d\u8981\u7740\u6025\u95ee\u53f7\u8fd9\u5c31\u6765\u4e86\u3002<\/p>\n
\u5728OC\u4e2d\u5982\u679c\u67d0\u4e2a\u53d8\u91cf\u662fnil\u65f6\uff0c\u8c03\u7528\u8fd9\u4e2a\u53d8\u91cf\u5219\u4f1a\u65e0\u4e8b\u53d1\u751f\uff0cSwift\u4e2d\u4e5f\u63d0\u4f9b\u4e86\u4e00\u4e2a\u7c7b\u4f3c\u7684\u673a\u5236\uff0c\u90a3\u5c31\u662fOptional\u7684\u95ee\u53f7\u64cd\u4f5c\u7b26\uff0c\u4f7f\u7528\u95ee\u53f7\u64cd\u4f5c\u7b26\u5bf9Optional\u4e2d\u7684\u5bf9\u8c61\u8fdb\u884c\u64cd\u4f5c\u5c31\u6784\u6210\u4e86\u4e00\u4e2a\u53ef\u9009\u94fe\u3002<\/p>\n
class ListNode {\r\n\u00a0 var text: String\r\n\u00a0 var next: ListNode?\r\n}\r\n\r\n...\r\n\r\nfunc testOptionalChaining(node: ListNode?) {\r\n\u00a0 let thirdValue = node?.next?.next?.text\r\n\u00a0 if let text = thirdValue {\r\n\u00a0 \u00a0 printCount(of: text)\r\n\u00a0 } else {\r\n\u00a0 \u00a0 print(\"thirdValue is nil\")\r\n\u00a0 }\r\n}<\/pre>\n\u4e0a\u8fb9\u7684\u4ee3\u7801\u4e2d\u4f7f\u7528\u4e86\u95ee\u53f7\u64cd\u4f5c\u7b26\u5e76\u8c03\u7528\u4e86node\u7684next\u5c5e\u6027\uff0c\u95ee\u53f7\u64cd\u4f5c\u7b26\u4f1a\u5148\u5224\u65ad\u8be5node\u662f\u5426\u4e3anil\uff0c\u5982\u679c\u4e0d\u4e3anil\u5219\u89e3\u5305\u5e76\u7ee7\u7eed\u6267\u884c\uff0c\u5982\u679c\u662fnil\u5219\u4f1a\u6253\u65ad\u5f53\u524d\u7684\u53ef\u9009\u94fe\u5e76\u8fd4\u56denil\uff0c\u6240\u4ee5\u867d\u7136ListNode\u7c7b\u4e2d\u7684text\u5c5e\u6027\u4e0d\u662fOptional\u7c7b\u578b\uff0c\u4f46`node?.next?.next?.text`\u7684\u8fd4\u56de\u503c\u7684\u5374\u662fOptional\u7684\u3002<\/p>\n
\u4e3a\u4e86\u5c55\u793a\u53ef\u9009\u94fe\u88ab\u6253\u65ad\u7684\u60c5\u51b5\uff0c\u6211\u4eec\u7ed9ListNode\u7c7b\u589e\u52a0\u4e00\u4e2a\u65b9\u6cd5\u5e76\u6d4b\u8bd5\u4e00\u4e0b\uff0c\u770b\u4e00\u4e0b\u7ed3\u679c\u5982\u4f55\u3002<\/p>\n
class ListNode {\r\n\u00a0 var text: String\r\n\u00a0 var next: ListNode?\r\n\u00a0 func printTestAndGoNext() -> ListNode? {\r\n\u00a0 \u00a0 \/\/ \u5728\u5f53\u524d\u65b9\u6cd5\u4e2d\u6253\u5370text\u7684\u503c\u5e76\u8fd4\u56denext\u8282\u70b9\r\n\u00a0 \u00a0 print(\"----node value----\")\r\n\u00a0 \u00a0 print(self.text)\r\n\u00a0 \u00a0 return self.next\r\n\u00a0 }\r\n}\r\n\r\nfunc testBreakOptionalChaining(node: ListNode?) {\r\n\u00a0 node?.printTextAndGoNext()?.printTextAndGoNext()?.printTextAndGoNext().?printTextAndGoNext()\r\n}<\/pre>\n\u8c03\u7528testBreakOptionalChaining\u5e76\u4e14\u4f20\u5165\u4e86\u4e00\u4e2a\u94fe\u8868\u7684\u5934\u8282\u70b9\uff0c\u8be5\u94fe\u8868\u53ea\u6709\u4e24\u4e2a\u8282\u70b9\uff0c\u7b2c\u4e00\u4e2a\u8282\u70b9\u7684text\u503c\u4e3a”a”\uff0c\u7b2c\u4e8c\u4e2a\u8282\u70b9\u7684text\u503c\u4e3a”b”\uff0c\u6b64\u65f6\u63a7\u5236\u53f0\u8f93\u51fa\u5982\u4e0b\u3002<\/p>\n
----node value----\r\na\r\n----node value----\r\nb<\/pre>\n\u867d\u7136\u5728\u4ee3\u7801\u4e2d\u94fe\u5f0f\u8c03\u7528\u4e86\u56db\u6b21`printTextAndGoNext`\u65b9\u6cd5\uff0c\u4f46\u662f\u63a7\u5236\u53f0\u4e2d\u690d\u8f93\u51fa\u4e86\u4e24\u4e2a\u503c\uff0c\u56e0\u4e3a\u7b2c\u4e8c\u4e2a\u8282\u70b9\u7684next\u8282\u70b9\u4e3anil\uff0c\u6240\u4ee5\u5b9e\u9645\u4e0a\u540e\u8fb9\u7684\u4e24\u6b21\u8c03\u7528\u5e76\u6ca1\u6709\u88ab\u6267\u884c\uff0c\u8fd9\u4e2a\u53ef\u9009\u94fe\u88ab\u6253\u65ad\u4e86\u3002<\/p>\n
\u95ee\u53f7\u53f9\u53f7\u5c0f\u5267\u573a<\/h2>\n
\u4e0a\u6587\u4e2d\u4ecb\u7ecd\u4e86\u4f7f\u7528\u53f9\u53f7\u8fdb\u884c\u5f3a\u5236\u89e3\u5305\u548c\u4f7f\u7528\u95ee\u53f7\u6765\u5199\u4e00\u4e2a\u53ef\u9009\u94fe\uff0c\u4f46\u5176\u5b9e\u95ee\u53f7\u548c\u53f9\u53f7\u9664\u4e86\u5728\u8fd9\u4e24\u4e2a\u5730\u65b9\u4f1a\u88ab\u7528\u5230\uff0c\u5728\u58f0\u660e\u4e00\u4e2aOptional\u7c7b\u578b\u7684\u65f6\u5019\u4e5f\u53ef\u4ee5\u4f7f\u7528\u95ee\u53f7\u548c\u53f9\u53f7\uff0c\u4e0b\u9762\u662f\u58f0\u660eOptional\u7c7b\u578b\u7684\u51e0\u79cd\u65b9\u5f0f\u3002<\/p>\n
\/\/ \u65b9\u6cd51: \u76f4\u63a5\u58f0\u660e\u4e00\u4e2aOptional<String>\u7c7b\u578b\u7684\u53d8\u91cf\uff0c\u9700\u8981\u624b\u52a8\u63d0\u4f9b\u9ed8\u8ba4\u503c\r\nvar text1: Optional<String> = nil\r\n\/\/ \u65b9\u6cd52: \u4f7f\u7528\u7c7b\u578b+\u95ee\u53f7\u58f0\u660e\u4e00\u4e2aOptional\u7c7b\u578b\u53d8\u91cf\uff0c\u9ed8\u8ba4\u503c\u4e3anil\r\nvar text2: String?\r\n\/\/ \u65b9\u6cd53: \u4f7f\u7528\u7c7b\u578b+\u53f9\u53f7\u58f0\u660e\u4e00\u4e2aOptional\u7c7b\u578b\u53d8\u91cf\uff0c\u9ed8\u8ba4\u503c\u4e3anil\r\nvar text3: String!<\/pre>\n\u5728\u5f00\u53d1\u4e2d\u5e76\u4e0d\u5efa\u8bae\u4f7f\u7528\u65b9\u5f0f1\u6765\u58f0\u660eOptional\u7c7b\u578b\uff0c\u5e94\u8be5\u4f7f\u7528Swift\u63d0\u4f9b\u7684\u201c\u7c7b\u578b+\u95ee\u53f7\/\u53f9\u53f7\u201d\u58f0\u660eOptional\u7c7b\u578b\u7684\u8bed\u6cd5\u7cd6\u3002<\/p>\n
\u5728\u58f0\u660eOptional\u7c7b\u578b\u7684\u53d8\u91cf\u65f6\uff0c\u95ee\u53f7\u548c\u53f9\u53f7\u7684\u6548\u679c\u4e5f\u662f\u4e0d\u4e00\u6837\u7684\uff0c\u4f7f\u7528\u95ee\u53f7\u58f0\u660e\u7684\u6548\u679c\u4e0e\u65b9\u6cd51\u7b49\u540c\uff0c\u4f7f\u7528\u53f9\u53f7\u58f0\u660e\u5219\u6709\u4e00\u4e9b\u5c0f\u5c0f\u7684\u5dee\u522b\uff0c\u4f7f\u7528\u53f9\u53f7\u58f0\u660e\u7684Optional\u7c7b\u578b\uff0c\u5728\u88ab\u8c03\u7528\u65f6\u9ed8\u8ba4\u4f1a\u88ab\u5f3a\u5236\u89e3\u5305\u3002<\/p>\n
print(text1?.count) \/\/ \u8f93\u51fanil\r\nprint(text2?.count) \/\/ \u8f93\u51fanil\r\nprint(text3.count) \/\/ \u5bf9text3\u5f3a\u5236\u89e3\u5305\uff0c\u5e94\u7528crash<\/pre>\n\u56e0\u6b64\u4f7f\u7528\u201c\u7c7b\u578b+\u53f9\u53f7\u201d\u58f0\u660eOptional\u7c7b\u578b\u7684\u65b9\u5f0f\u5728\u5b9e\u9645\u5f00\u53d1\u4e2d\u5e94\u5f53\u8c28\u614e\u4f7f\u7528\uff0c\u5f53\u7136\u4e5f\u4e0d\u662f\u8bf4\u5b8c\u5168\u4e0d\u80fd\u7528\uff0c\u603b\u7ed3\u4e00\u4e0b\uff0c\u5982\u679c\u67d0\u4e2a\u53d8\u91cf\/\u5c5e\u6027\u5728\u4f7f\u7528\u65f6\u968f\u65f6\u53ef\u80fd\u4e3anil\uff0c\u90a3\u4e48\u5c31\u5e94\u8be5\u4f7f\u7528\u201c\u7c7b\u578b+\u95ee\u53f7\u201d\u6765\u58f0\u660e\uff1b\u5982\u679c\u67d0\u4e2a\u53d8\u91cf\/\u5c5e\u6027\u5728\u5f00\u59cb\u7684\u65f6\u5019\u53ef\u80fd\u4e3anil\uff0c\u4f46\u662f\u540e\u7eed\u4f7f\u7528\u7684\u65f6\u5019\u5fc5\u5b9a\u4f1a\u6709\u503c\uff0c\u90a3\u4e48\u5c31\u53ef\u4ee5\u4f7f\u7528\u201c\u7c7b\u578b+\u53f9\u53f7\u201d\u6765\u58f0\u660e\u3002<\/p>\n
Tips\uff1aUIViewController\u7684view\u5c5e\u6027\u5c31\u662f\u4f7f\u7528\u53f9\u53f7\u58f0\u660e\u7684\uff08`var<\/b> view: UIView!`)\uff0c\u5728init\u65f6\u5019\u4e3anil\uff0c\u4f46\u662f\u968f\u540e\u6267\u884cloadView\u540e\u5c31\u6709\u4e86\u503c\u3002<\/p>\n
\u7ed3\u8bed<\/h2>\n
\u8bf4\u4e86\u90a3\u4e48\u591a\uff0c\u5176\u5b9eOptional\u5f88\u7b80\u5355\uff0c\u5b83\u5c31\u50cf\u662f\u4e00\u4e2a\u7bb1\u5b50\uff0c\u5728\u6253\u5f00\u7bb1\u5b50\u4e4b\u524d\u4f60\u4e0d\u77e5\u9053\u91cc\u9762\u6709\u6ca1\u6709\u4e1c\u897f\uff0c\u4f7f\u7528\u95ee\u53f7\u5c31\u76f8\u5f53\u4e8e\u544a\u8bc9\u4f60\u7bb1\u5b50\u91cc\u53ef\u80fd\u6709\u4e1c\u897f\u4e5f\u53ef\u80fd\u4ec0\u4e48\u4e5f\u6ca1\u6709\uff0c\u6240\u4ee5\u4f60\u5728\u6253\u5f00\u7684\u65f6\u5019\u9700\u8981\u68c0\u67e5\u4e00\u4e0b\u5230\u5e95\u662f\u6709\u8fd8\u662f\u6ca1\u6709\uff0c\u800c\u4f7f\u7528\u53f9\u53f7\u5c31\u76f8\u5f53\u4e8e\u544a\u8bc9\u4f60\u8fd9\u4e2a\u7bb1\u5b50\u91cc\u662f\u6709\u4e1c\u897f\u7684\uff0c\u6253\u5f00\u7684\u65f6\u5019\u4e0d\u9700\u8981\u68c0\u67e5\u4e86\uff0c\u6240\u4ee5\u4f60\u6253\u5f00\u7bb1\u5b50\u7684\u65f6\u5019\u770b\u5230\u7a7a\u7a7a\u5982\u4e5f\u7684\u7bb1\u5b50\u5c31\u4f1a\u4ea7\u751f\u6df7\u4e71\uff08\u8fd0\u884c\u65f6\u9519\u8bef\uff09\uff0c\u5e76\u4e0d\u77e5\u9053\u8fd9\u7bb1\u5b50\u91cc\u7684\u4e1c\u897f\u662f\u88ab\u5077\u4e86\u8fd8\u662f\u5bf9\u65b9\u9a97\u4e86\u4f60\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u5b66\u4e60Swift\u65f6\uff0c\u7edd\u5927\u591a\u6570\u521d\u5b66\u8005\u90fd\u4f1a\u88abSwift\u4e2d\u7684Optional\u8fd9\u4e2a\u7c7b\u578b\u6240\u56f0\u6270\uff0c\u6bd4\u5982\u201c\u95ee\u53f7\u662f\u4ec0\u4e48\uff1f\u201d\u3001\u201c\u53f9 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"_links":{"self":[{"href":"https:\/\/flykite.me\/index.php?rest_route=\/wp\/v2\/posts\/73"}],"collection":[{"href":"https:\/\/flykite.me\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/flykite.me\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/flykite.me\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/flykite.me\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=73"}],"version-history":[{"count":1,"href":"https:\/\/flykite.me\/index.php?rest_route=\/wp\/v2\/posts\/73\/revisions"}],"predecessor-version":[{"id":79,"href":"https:\/\/flykite.me\/index.php?rest_route=\/wp\/v2\/posts\/73\/revisions\/79"}],"wp:attachment":[{"href":"https:\/\/flykite.me\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=73"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/flykite.me\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=73"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/flykite.me\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=73"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}