在Objective-C中,我可以在一个浮点数的c数组上声明@property吗？

Question

thing.h

@interface Thing : NSObject 
{
     float stuff[30];
}

@property float stuff;
@end

thing.m

@implementation Thing
@synthesize stuff;
@end

我收到错误:属性'stuff'的类型与ivar'stuff'的类型不匹配

我不想使用NSArray,因为我必须将浮点数变成NSNumber(对吗？),这对于数学运算来说是一种痛苦.

更新:我注意到类似的答案有猜测和试验答案.虽然我很欣赏非Objective-C人员的尝试,但我希望得到一个明确的答案是否有可能.

Answer 1

好的,我编译了以下代码,它按预期工作.

FloatHolder.h

@interface FloatHolder : NSObject {
    int _count;
    float* _values;
}

- (id) initWithCount:(int)count;

// possibly look into this for making access shorter
// http://vgable.com/blog/2009/05/15/concise-nsdictionary-and-nsarray-lookup/
- (float)getValueAtIndex:(int)index;
- (void)setValue:(float)value atIndex:(int)index;

@property(readonly) int count;
@property(readonly) float* values; // allows direct unsafe access to the values

@end

FloatHolder.m

#import "FloatHolder.h"


@implementation FloatHolder

@synthesize count = _count;
@synthesize values = _values;

- (id) initWithCount:(int)count {
    self = [super init];
    if (self != nil) {
        _count = count;
        _values = malloc(sizeof(float)*count);
    }
    return self;
}

- (void) dealloc
{
    free(_values);

    [super dealloc];
}

- (float)getValueAtIndex:(int)index {
    if(index<0 || index>=_count) {
        @throw [NSException exceptionWithName: @"Exception" reason: @"Index out of bounds" userInfo: nil];
    }

    return _values[index];
}

- (void)setValue:(float)value atIndex:(int)index {
    if(index<0 || index>=_count) {
        @throw [NSException exceptionWithName: @"Exception" reason: @"Index out of bounds" userInfo: nil];
    }

    _values[index] = value;
}

@end

然后在您的其他应用程序代码中,您可以执行以下操作:

**FloatTestCode.h**

#import <Cocoa/Cocoa.h>
#import "FloatHolder.h"

@interface FloatTestCode : NSObject {
    FloatHolder* holder;
}

- (void) doIt:(id)sender;

@end

**FloatTestCode.m**

#import "FloatTestCode.h"


@implementation FloatTestCode

- (id) init
{
    self = [super init];
    if (self != nil) {
        holder = [[[FloatHolder alloc] initWithCount: 10] retain];
    }
    return self;
}

- (void) dealloc
{
    [holder release];

    [super dealloc];
}

- (void) doIt:(id)sender {
    holder.values[1] = 10;
}

Answer 2

属性的类型必须与它将存储的实例变量的类型相匹配,因此您可以执行类似的操作

  @interface Thing : NSObject 
  {
       float stuff[30];
  }

  @property float[30] stuff;
  @end

它应该工作.我不会推荐它.我猜你正在寻找类似Delphi索引属性的东西.你得到的最接近的是如下.

  @interface Thing : NSObject 
  {
       float stuff[30];
  }

  - (void) setStuff:(float)value atIndex:(int)index;
  - (float) getStuffAtIndex:(int)index;
  @end