目标c：传递一个char参数的函数会崩溃的应用程序 [英] objective c: passing a char argument to function crashes the app

问题描述

我写了一个名为SomeValues的单例，其中我初始化一个foo NSMutableArray。然后我尝试写一个函数SetBFSV从不同的控制视图设置此数组的值。

  @interface SomeValues：NSObject { 
 NSMutableArray * foo;} 
 +（SomeValues *）sharedInstance; 
 
 @implementation 
 
 ... 
 
  - （void）SetBFSV：（char）lbl ToVal：（long）BFSvl {
 NSNumber * ValueBFSvl = [NSNumber numberWithLong：BFSvl]; 
 NSString * Strlbl = [[NSString alloc] stringWithFormat：@％s，lbl]; 
 [foo setValue：ValueBFSvl forKey：Strlbl]; 
} 
  

我知道setValue需要一个NS对象的值和键，但我不能将我的函数声明为

 （void）SetBFSV：（NSString）lbl ToVal：（NSNumber）BFSvl 
  

因为它不编译时出现错误：无法使用对象作为方法的参数 p>

在一个ControlView中我写了这段代码：

  SomeValues * myBFSV = [SomeValues sharedInstance]; 
 const unsigned char * Bar =（unsigned char *）[@Label1UTF8String]; 
 NSLog（@字符串％s，Bar）; 
 [myBFSV SetBFSV：Bar ToVal：2.5]; 
  

在编译时，我在最后一行得到警告：

警告：SetBFSV：ToVal：的传递参数1从无指针的指针中获取整数

我越来越愚蠢的环顾四周。当运行我从NSLog打印输出，但紧接着程序显然崩溃与此错误：

'NSInvalidArgumentException'，reason：' - [NSPlaceholderString stringWithFormat：] ：无法识别的选择器发送到实例0x4e03280'

显然，我向stringWithFormat传递错误，但我不明白。

感谢任何帮助。有一个愉快的一天！

/ luca

解决方案

您不能使用对象作为参数：

 （void）SetBFSV：（NSString）lbl ToVal：（NSNumber）BFSvl 
  

您需要使用星号作为指针传递。

 （void）SetBFSV：（NSString *）lbl ToVal：（NSNumber *）BFSvl 
   
 
此外，如果你需要传递（char）和（long）您的位代码：
  SomeValues * myBFSV = [SomeValues sharedInstance]; 
 const unsigned char * Bar =（unsigned char *）[@Label1UTF8String]; 
 NSLog（@字符串％s，Bar）; 
 [myBFSV SetBFSV：Bar ToVal：2.5]; //在任何一种情况下，这是一个长。你为什么在这里传递一个双？ 
  
以指针形式传递 * Bar 你应该真正阅读指针和对象。如果你需要以（const char *）和（long）的方式传递它们， p> 
 
 
   - （void）SetBFSV：（const char *）lbl ToVal：（long）BFSvl {
 NSNumber * ValueBFSvl = NSNumber numberWithLong：BFSvl]; 
 NSString * Strlbl = [NSString stringWithUTF8String：lbl]; //你的旧代码在这里有一个内存泄漏。你需要创建一个autorelease对象，或者在添加到`foo`后释放它
 [foo setValue：ValueBFSvl forKey：Strlbl]; 
} 
  
我的建议是执行以下操作：
   - （void）SetBFSV：（NSString *）key ToVal：（long）val {
 NSNumber * value = [NSNumber numberWithLong：val]; 
 [foo setValue：value forKey：key]; 
} 
  
并像下面这样调用（从你的例子）：
  SomeValues * myBFSV = [SomeValues sharedInstance]; 
 NSString * Bar = [NSString stringWithString：@Label1]; //这可能不是必须的.​​.. 
 NSLog（@字符串％@，Bar）; 
 [myBFSV SetBFSV：Bar ToVal：25]; //不传递小数（长）
  
 
I wrote a singleton called SomeValues where I initialize a foo NSMutableArray. I then tried to write a function SetBFSV to set the values of this array from different control views.
@interface SomeValues : NSObject {
NSMutableArray *foo;}
+ (SomeValues *) sharedInstance;

@implementation

...

- (void) SetBFSV:(char)lbl ToVal:(long)BFSvl{
NSNumber *ValueBFSvl = [NSNumber numberWithLong:BFSvl];
NSString *Strlbl = [[NSString alloc] stringWithFormat:@"%s",lbl];
[foo setValue:ValueBFSvl forKey:Strlbl];
}
I know that setValue requires a NS object for both the value and the key, but I cannot declare my function as
(void) SetBFSV:(NSString)lbl ToVal:(NSNumber)BFSvl
because it doesn't compile with the error: "Can not use an object as parameter to a method".

In one ControlView I wrote then this piece of code:
SomeValues *myBFSV = [SomeValues sharedInstance];
const unsigned char *Bar = (unsigned char *)[@"Label1" UTF8String];
NSLog(@"The string %s", Bar);
[myBFSV SetBFSV:Bar ToVal:2.5];
When compiling I get a warning on the last line:

warning: passing argument 1 of 'SetBFSV:ToVal:' makes integer from pointer without a cast

Which integer? I'm getting stupid looking around for it. When running I get the print out from the NSLog, but right afterwards the program obviously crashes with this error:

'NSInvalidArgumentException', reason: '-[NSPlaceholderString stringWithFormat:]: unrecognized selector sent to instance 0x4e03280'

Clearly I'm passing something wrong to stringWithFormat but I cannot understand what.

Thanks for any help. Have a nice day!

/luca
解决方案
For one, you can't use an object as a paramter:
(void) SetBFSV:(NSString)lbl ToVal:(NSNumber)BFSvl
You need to pass them as pointers, using the asterisk.
(void) SetBFSV:(NSString*)lbl ToVal:(NSNumber*)BFSvl
Furthermore, if you need to pass them as (char) and (long) your bit of code:
SomeValues *myBFSV = [SomeValues sharedInstance];
const unsigned char *Bar = (unsigned char *)[@"Label1" UTF8String];
NSLog(@"The string %s", Bar);
[myBFSV SetBFSV:Bar ToVal:2.5];  // in either case, this is a long.  why are you passing a double here?
Passes *Bar as a pointer.  You should really read up on the pointers and objects.  IF you need to pass them in as (const char*) and (long) do it like this:
- (void) SetBFSV:(const char*)lbl ToVal:(long)BFSvl{
NSNumber *ValueBFSvl = [NSNumber numberWithLong:BFSvl];
NSString *Strlbl = [NSString stringWithUTF8String: lbl]; // your old code had a memory leak here.  you need to either create an autorelease object, or release it after adding to `foo`
[foo setValue:ValueBFSvl forKey:Strlbl];
}
My Recommendation is to do the following:
- (void) SetBFSV:(NSString*)key ToVal:(long)val{
    NSNumber *value = [NSNumber numberWithLong:val];
    [foo setValue:value forKey:key];
}
And call it like the following (from your example):
SomeValues *myBFSV = [SomeValues sharedInstance];
NSString *Bar = [NSString stringWithString:@"Label1"];// this may not be necessary...
NSLog(@"The string %@", Bar);
[myBFSV SetBFSV:Bar ToVal:25]; // don't pass a decimal for a (long)


                        
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