如何转储存储在 Objective-c 对象（NSArray 或 NSDictionary）中的数据
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How to dump data stored in objective-c object (NSArray or NSDictionary)
提问by jpm
Forgive me for a potentially silly question here, but in other programming languages (scripting ones like PHP or Perl) it is often easy to dump everything contained within a variable.
请原谅我在这里提出一个潜在的愚蠢问题，但在其他编程语言（PHP 或 Perl 等脚本语言）中，通常很容易转储变量中包含的所有内容。
For instance, in PHP there are the var_dump()or print_r()functions. Perl has the Data::DumperCPAN class, etc etc.
例如，在 PHP 中有var_dump()orprint_r()函数。Perl 有Data::DumperCPAN 类等等。
Is there something like this for Objective-C? It would be very convenient in a few cases to be able to dump everything like that, instead of using gdb to inspect each variable.
Objective-C 有类似的东西吗？在某些情况下，能够像这样转储所有内容，而不是使用 gdb 来检查每个变量会非常方便。
回答by Barry Wark
In Cocoa, there is no "dump" like PHP's print_r or python's reprsince there is no textual format that "represents" an object as in those languages. If you use
在 Cocoa 中，没有像 PHP 的 print_r 或 python 的repr那样的“转储”，因为没有像在这些语言中那样“表示”对象的文本格式。如果你使用
NSLog(@"%@", myObj);
or
或者
NSString *stringRep = [NSString stringWithFormat:@"%@",myObj];
or
或者
NSString *stringRep = [myObj description];
you will get (logged to console in the first case), the result of [myObj description], a method defined in NSObjectfor the purpose of printing a description(nota dump) of an object.
您将获得（在第一种情况下登录到控制台）的结果[myObj description]，在 中定义的方法NSObject用于打印对象的描述（而不是转储）。
If you invoke po myObjin gdb, you get [myObj debugDescription](often the same as description, but not always).
如果您po myObj在 gdb 中调用，您会得到[myObj debugDescription]（通常与 相同description，但并非总是如此）。
Classes like NSArrayand NSDictionaryand NSDataoverride descriptionto print a pretty useful recursive description of their contents, but the default [NSObject description]prints only the pointer value corresponding to the instance.
像NSArrayandNSDictionary和NSDataoverride 之类的类description可以打印非常有用的对其内容的递归描述，但默认值[NSObject description]仅打印与实例对应的指针值。
If you control the code for the types in question, you can override their descriptionor debugDescriptionmethods to return anything you want. If not, you could override the descriptionor debugDescriptionmethod using a category, or use a category to define a myDebugDescriptionor some such that you could then invoke from gdb using po [myObj myDebugDescription].
如果您控制相关类型的代码，您可以覆盖它们的description或debugDescription方法以返回您想要的任何内容。如果没有，您可以使用类别覆盖descriptionordebugDescription方法，或者使用类别定义 amyDebugDescription或 some 以便您可以使用po [myObj myDebugDescription].
回答by Ben Gottlieb
you can also use the gdb print object command to quickly view an object in the debugger:
您还可以使用 gdb 打印对象命令在调试器中快速查看对象：
po dictionary
This will be basically the same as calling NSLog(...) from within your code.
这与在代码中调用 NSLog(...) 基本相同。
Also useful when printing out NSData that contains ASCII data is:
在打印出包含 ASCII 数据的 NSData 时也很有用：
p (char *) [data bytes]
回答by Jason Coco
Use NSLog() to dump contents of objects. For example:
使用 NSLog() 转储对象的内容。例如：
NSData* myData = //... assume this exists
NSLog(@"Contents of myData: %@", myData);
NSLog has a printf-style format string (expects an NSString object) followed by a variable list of parameters, just like printf. The replacement character %@ represents an object the description method on an object. This is useful for dumping most Objective-C objects in Cocoa.
NSLog 有一个 printf 风格的格式字符串（需要一个 NSString 对象），后跟一个变量列表，就像 printf 一样。替换字符 %@ 代表一个对象，一个对象的描述方法。这对于在 Cocoa 中转储大多数 Objective-C 对象很有用。
If you want to dump the contents of an object using gdb (I see you tagged this with gdb), use the special "po" directive instead of print. For example:
如果您想使用 gdb 转储对象的内容（我看到您用 gdb 标记了它），请使用特殊的“po”指令而不是打印。例如：
gdb) po myData
will cause gdb to dump the myData object. po is a shortcut for print-object.
将导致 gdb 转储 myData 对象。po 是打印对象的快捷方式。
回答by diciu
Be careful with NSLog logging -> you most likely don't want it in production code.
小心 NSLog 日志记录 -> 您很可能不希望在生产代码中使用它。
You may want to use an alternate logging function that calls NSLog when your product is running in debug mode.
当您的产品在调试模式下运行时，您可能希望使用调用 NSLog 的备用日志记录功能。
回答by TCB13
I usualy go with this to "debug" NSArray contents:
我通常用它来“调试” NSArray 内容：
NSEnumerator *arrenum = [myarray objectEnumerator];
id cobj;
while ( cobj = [arrenum nextObject] ) {
NSLog(@"%@", cobj);
}
The code will enumerate all objects in the NSArray myarray, and then iterate through and print every object.
代码将枚举 NSArray 中的所有对象myarray，然后遍历并打印每个对象。
Hope this can be useful for someone!
希望这对某人有用！
