在 Objective-C 中，我可以在浮点数 c 数组上声明 @property 吗? [英] In Objective-C, can I declare @property on a c-array of floats?

问题描述

东西.h

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

@property float stuff;
@end

东西.m

@implementation Thing
@synthesize stuff;
@end

我收到错误:属性stuff"的类型与 ivarstuff"的类型不匹配

我不想使用 NSArray，因为我必须将浮点数转换为 NSNumbers(对吗?)，用它做数学很麻烦.

I don't want to use an NSArray because I'd have to make the floats into NSNumbers (right?) and that's a pain to do math with.

更新:我注意到类似的答案有猜测和试用答案.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，无论是否可行.

Update: I've noticed similar answers had guesses and trial answers. While I appreciate the attempts by non-Objective-C folks, I'm hoping for a definitive answer whether it's possible or not.

推荐答案

好的，我已经编译了以下代码，它按预期工作.

OK, I have compiled up the following code at it works as expected.

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:

then in your other application code you can do something like the following:

** FloatTestCode.h **

** FloatTestCode.h **

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

@interface FloatTestCode : NSObject {
    FloatHolder* holder;
}

- (void) doIt:(id)sender;

@end

** FloatTestCode.m **

** 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;
}

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