正确的方式转换char *到NSString没有initWithCString？ [英] Proper way to convert char* to NSString without initWithCString?

问题描述

我正在从SQLite3数据库的结果列表到 UITableView 。我从数据库中拉取文本的代码如下：

  char * menuNameChars =（char *）sqlite3_column_text ）; 
 NSString * menuName = [[NSString alloc] initWithUTF8String：menuNameChars]; 
 NSLog（@Retrieved％s，％@ from DB。，menuNameChars，menuName）; 
  

当我使用 initWithUTF8String 是从数据库正确复制。有时候，信息从 char * 正确显示，但不能从 NSString ：

  2011-10-24 22：26：54.325 [23974：207]从DB回收Cravin鸡肉三明治 - 
 2011-10-24 22：26：54.327 [23974：207]检索的Cravin鸡肉三明治 - 烤，（null）从DB。 
 2011-10-24 22：26：54.331 [23974：207]从DB取回Jr鸡肉三明治，Jr鸡肉三明治。 
 2011-10-24 22：26：54.337 [23974：207]检索的Prime-Cut鸡招标 -  3件，Prime-Cut鸡招标 -  3件从DB。现在，如果我用 initWithUTF8String 替换 



initWithCString ，代码工作完美。然而，XCode 4.2告诉我， initWithCString 已被弃用。我知道足够了解我不想使用弃用的代码，但如果 initWithUTF8String 不工作，我应该使用什么？

我可以看到你的第一个日志行中的破折号（ Retrieved Cravin Chicken Sandwich ... ）不是一个简单的ASCII HYPHEN-MINUS （U + 002D，UTF-8 2D）。它是一个Unicode EN DASH 字符（U + 2013，UTF-8 E2 80 93）。第二行也相同。我的猜测是他们在您的数据库中编码不正确。如果你给 - [NSString initWithUTF8String：] 一个不是有效UTF-8的C字符串，它会返回 nil 。

尝试打印 menuNameChars 的十六进制转储。你可以通过在调用 sqlite3_column_text 之后在行上设置断点来实现。当到达断点时，右键单击/控制单击在您的堆栈框架窗口中的 menuNameChars ，并选择查看* menuNameChars的内存（注意 * ）。

I'm pulling a listing of results from a SQLite3 database into a UITableView. The code where I pull text from the database is like so:

char *menuNameChars = (char *) sqlite3_column_text(statement, 1);
NSString *menuName = [[NSString alloc] initWithUTF8String:menuNameChars];
NSLog(@"Retrieved %s,%@ from DB.", menuNameChars, menuName);

When I use initWithUTF8String, sometimes the information is copied properly from the database. Sometimes though, the information is displayed properly from the char*, but not from the NSString:

2011-10-24 22:26:54.325 [23974:207] Retrieved Cravin Chicken Sandwich – Crispy, (null) from DB.
2011-10-24 22:26:54.327 [23974:207] Retrieved Cravin Chicken Sandwich – Roast, (null) from DB.
2011-10-24 22:26:54.331 [23974:207] Retrieved Jr Chicken Sandwich, Jr Chicken Sandwich from DB.
2011-10-24 22:26:54.337 [23974:207] Retrieved Prime-Cut Chicken Tenders - 3 Piece, Prime-Cut Chicken Tenders - 3 Piece from DB.

Now, if I replace initWithUTF8String with initWithCString, the code works perfectly. However, XCode 4.2 tells me that initWithCString has been deprecated. I know enough to understand I don't want to use deprecated code, but if initWithUTF8String isn't working, what should I use?

解决方案

(edited)

I can see that the dash in your first log line (Retrieved Cravin Chicken Sandwich ...) isn't a simple ASCII HYPHEN-MINUS (U+002D, UTF-8 2D). It's a Unicode EN DASH character (U+2013, UTF-8 E2 80 93). Same for the second line. My guess is they're encoded incorrectly in your database. If you give -[NSString initWithUTF8String:] a C-string that's not valid UTF-8, it returns nil.

Try printing a hex dump of menuNameChars. You can do that by setting a breakpoint on the line after the call to sqlite3_column_text. When the breakpoint is reached, right-click/control-click menuNameChars in your stack frame window and choose View memory of "*menuNameChars" (note the *).

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