目標C - 與存檔麻煩編碼和解碼

Question

我正在學習的Objective-C的時刻，到歸檔和卡住了與編碼和解碼。

這裏是我的代碼。

#import <Foundation/Foundation.h> 

    @interface Foo : NSObject<NSCoding> 

    @property (copy, nonatomic) NSString *strVal; 
    @property int intVal; 
    @property float floatVal; 

    @end 

    #import "Foo.h" 

@implementation Foo 

@synthesize intVal, floatVal, strVal; 

-(void) encodeWithCoder: (NSCoder *) encoder 
{ 
    [encoder encodeObject: strVal forKey: @"test1"]; 
    [encoder encodeInt: intVal forKey: @"test2"]; 
    [encoder encodeFloat: floatVal forKey: @"test3"]; 
} 

-(id) initWithCoder: (NSCoder *) decoder 
{ 
    strVal = [decoder decodeObjectForKey: @"test1"]; 
    intVal = [decoder decodeIntForKey: @"test2"]; 
    floatVal = [decoder decodeFloatForKey: @"test3"]; 

    return self; 
} 

@end 


    #import "Foo.h" 

    int main (int argc, const char * argv[]) 
    { 

     @autoreleasepool { 
      Foo *myFoo1 = [[Foo alloc] init]; 
      Foo *myFoo2; 

      [myFoo1 setStrVal : @"bill"]; 
      [myFoo1 setIntVal : 2]; 
      [myFoo1 setFloatVal: 3.4]; 

      [NSKeyedArchiver archiveRootObject: myFoo1 toFile: @"foo.arch"]; 

      myFoo2 = [NSKeyedUnarchiver unarchiveObjectWithFile: @"foo.arch"]; 

      NSLog(@"%@", [myFoo2 strVal]); 
     } 
     return 0; 
    } 

該解碼適用於int和float，但是當我嘗試解碼NSString對象時。我得到了下面的錯誤，我對此毫無頭緒......

主題1：PROGRAME接收信號：EXC_BAD_ACESS」

GNU gdb 6.3.50-20050815 (Apple version gdb-1708) (Mon Aug 15 16:03:10 UTC 2011) 
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Current language: auto; currently objective-c 
(gdb) 

Answer 1

-initWithCoder:是一個初始化器的方法，在這裏你必須電話前[super init]設置你的對象。請參閱蘋果的「Archives and Seralizations Programming Guide」的例子。

Answer 2

是否使用ARC？

無論如何，你應該複製所有字符串（strValue = [[decoder decodeObjectForKey:@"test1"] copy];），以便保持對它們的不可變引用。否則，他們可以改變或消失在你的背後，事情將會變成kaboom（就像你看到的那樣）。

此外，像@一二三說，不要忘了self = [super init];。