Checking a null value in Objective-C that has been returned from a JSON string
I have a JSON object that is coming from a webserver. The log is something like this: { "status":"success", "UserID":15, "Name":"John", "DisplayName":"John", "Surname":"Smith", "Email":"email", "Telephone":null, "FullAccount":"true" } Note the Telephone is coming in as null if the user doesn't enter one. When assigning this value to a NSString, in the NSLog it's coming out as <null> I am assigning
null許容値型(Nullable<T> 型)
æ¦‚è¦ é€šå¸¸ã€ã€Œå€¤åž‹ã€ã¯ null 値（無効ãªå€¤ï¼‰ã‚’å–ã‚Œã¾ã›ã‚“。 ã¨ã“ã‚ãŒã€ãƒ‡ãƒ¼ã‚¿ãƒ™ãƒ¼ã‚¹ç‰ã€ä¸€éƒ¨ã®ã‚¢ãƒ—リケーションã§ã¯ã€ 値型ã®é€šå¸¸ã®ï¼ˆæœ‰åŠ¹ãªï¼‰å€¤ã¨ null（無効ãªå€¤ï¼‰ã‚’å–るよã†ãªåž‹ãŒæ¬²ã—ã„ã¨ããŒã‚ã‚Šã¾ã™ã€‚ ãã“ã§ã€C# 2.0 ã§ã¯ã€null 許容型（Nullable 型）ã¨ã„ã†ç‰¹æ®Šãªåž‹ãŒç”¨æ„ã•ã‚Œã¾ã—ãŸã€‚ Ver. 8.0 C# 8.0 ã§ã¯ã€å‚照型ã«ã¤ã„ã¦ã‚‚ ? ã®æœ‰ç„¡ã§ null ã®å¯å¦ã‚’指定ã™ã‚‹æ©Ÿèƒ½ãŒè¿½åŠ ã•ã‚Œã¾ã—ãŸã€‚ ã“ã®æ©Ÿèƒ½ã‚’指ã—㦠null 許容å‚照型(nullable reference type)ã¨è¨€ã£ãŸã‚Šã—ã¾ã™ã€‚ ã“ã® null 許容å‚照型ã¨åŒºåˆ¥ã™ã‚‹æ„味ã§ã€æœ¬é …ã§èª¬æ˜Žã—ã¦ã„る機能(C# 2.0 時代ã«ã¯å”¯ä¸€ã® null 許容型ã ã£ãŸ)を指ã—ã¦ã€null 許容値型(nullable value type)ã¨å‘¼ã¶ã“ã¨ã‚‚ã‚ã‚Šã¾ã™ã€‚ ãƒã‚¤ãƒ³ãƒˆ 値型 T ã«å¯¾ã—ã¦ã€T? ã‚’ã„ã†æ›¸ã
Nullable value types - C# reference
A nullable value type T? represents all values of its underlying value type T and an additional null value. For example, you can assign any of the following three values to a bool? variable: true, false, or null. An underlying value type T cannot be a nullable value type itself. Any nullable value type is an instance of the generic System.Nullable<T> structure. You can refer to a nullable value ty
Windows ã®åŸºæœ¬çš„ãªã‚³ãƒžãƒ³ãƒ‰é›† - IT戦記
ã¾ãšã¯ã€ã‚³ãƒžãƒ³ãƒ‰ãƒ—ãƒãƒ³ãƒ—トã®åŸºæœ¬çš„ãªéƒ¨åˆ†ã‚’使ãˆã‚‹ã‚ˆã†ã«ãªã‚‰ãªã„ã¨ã€‚。ã¨ã„ã†ã“ã¨ã§ nul ファイル Unix ã® /dev/null ã®ã‚ˆã†ãªã‚‚㮠サイレントã«ã‚³ãƒžãƒ³ãƒ‰ã‚’実行 > verbose-command > nul 空ã®ãƒ•ã‚¡ã‚¤ãƒ«ã‚’作る > type nul > hoge.txtã“ーんãªæ„Ÿã˜ã§ã‚³ãƒ”ーãŒã§ãã‚‹ 環境変数 PATH 〠PATHEXT PATH ã¨ã„ã†ç’°å¢ƒå¤‰æ•°ã«ãƒ‡ã‚£ãƒ¬ã‚¯ãƒˆãƒªã‚’登録ã—ã¦ãŠãã¨ã€ãã®ãƒ‡ã‚£ãƒ¬ã‚¯ãƒˆãƒªå†…ã®å®Ÿè¡Œãƒ•ã‚¡ã‚¤ãƒ«ï¼ˆç’°å¢ƒå¤‰æ•° PATHEXT ã§æŒ‡å®šã•ã‚ŒãŸæ‹¡å¼µåã‚’æŒã£ãŸãƒ•ã‚¡ã‚¤ãƒ«ï¼‰ãŒãƒ•ã‚¡ã‚¤ãƒ«åã ã‘ã§å®Ÿè¡Œã§ãるよã†ã«ãªã‚Šã¾ã™ã€‚ PATHEXT ã« .TXT を指定ã—ã¦ã¿ã‚‹ 以下ã®ã‚ˆã†ã«ã™ã‚‹ã¨ .txt ã«é–¢é€£ä»˜ã‘られãŸã‚¢ãƒ—リケーション（メモ帳）ã§ã€ hoge.txt ãŒèµ·å‹•ã™ã‚‹ã€‚ > type nul > hoge.txt > set PATHEXT = .TXT >
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