在arm64上使用NSScanner处理CGFloat

问题描述

显然，

<$ p $ p> #if defined（__ LP64__）&&& __LP64__
＃define CGFLOAT_TYPE double
＃define CGFLOAT_IS_DOUBLE 1
＃define CGFLOAT_MIN DBL_MIN
＃define CGFLOAT_MAX DBL_MAX
#else
＃define CGFLOAT_TYPE float
＃define CGFLOAT_IS_DOUBLE 0
＃define CGFLOAT_MIN FLT_MIN
＃define CGFLOAT_MAX FLT_MAX
#endif


所以代码

  NSScanner * scanner = [NSScanner scannerWithString：string]; 
 CGFloat c [components]; 
 [scanner scanFloat：& c [i]] 
  

位的应用程序，被打破为64位。它可以替换为

  NSScanner * scanner = [NSScanner scannerWithString：string]; 
 CGFloat c [components]; 
 #if CGFLOAT_IS_DOUBLE 
 [scanner ScanDouble：& c [i]]; 
 #else 
 [scanner scanFloat：& c [i]]; 
 #endif 
  

但是有更好的选择吗？

解决方案

NSScanner 只支持，所以你需要在某处放置#if指令。也就是说，如果你经常使用这个，你可以子类NSScanner或使用，使代码更加优雅。

我认为基于类别的代码看起来像：

NSScanner + MyAdditions.h：

  #importNSScanner.h
 
 @interface NSScanner（MyAdditions）
  - （BOOL）my_scanCGFloat：（CGFloat *）cgFloatValue 
 @end 
  

NSScanner + MyAdditions.m：

  #importNSScanner + MyAdditions .h
 
 @implementation NSScanner（MyAdditions）
  - （BOOL）my_scanCGFloat：（CGFloat *）cgFloatValue {
 #if CGFLOAT_IS_DOUBLE 
 return [self scanDouble：cgFloatValue ]; 
 #else 
 return [self scanFloat：cgFloatValue]; 
 #endif 
} 
 @end 
  

Apparently CGFloat is double on arm64:

#if defined(__LP64__) && __LP64__
# define CGFLOAT_TYPE double
# define CGFLOAT_IS_DOUBLE 1
# define CGFLOAT_MIN DBL_MIN
# define CGFLOAT_MAX DBL_MAX
#else
# define CGFLOAT_TYPE float
# define CGFLOAT_IS_DOUBLE 0
# define CGFLOAT_MIN FLT_MIN
# define CGFLOAT_MAX FLT_MAX
#endif

So the code

NSScanner *scanner = [NSScanner scannerWithString:string];
CGFloat c[components];
[scanner scanFloat:&c[i]]

which was working fine for 32-bit apps, is broken for 64-bit. It can be replaced with

NSScanner *scanner = [NSScanner scannerWithString:string];
CGFloat c[components];
#if CGFLOAT_IS_DOUBLE
   [scanner scanDouble:&c[i]];
#else
   [scanner scanFloat:&c[i]];
#endif

But is there a better alternative?

解决方案

NSScanner only supports a few basic types, so you're going to need to have that #if directive somewhere. That said, if you're using this often you could subclass NSScanner or use a category to make the code more elegant.

I think the category-based code would look something like:

NSScanner+MyAdditions.h:

#import "NSScanner.h"

@interface NSScanner (MyAdditions)
  - (BOOL)my_scanCGFloat:(CGFloat *) cgFloatValue
@end

NSScanner+MyAdditions.m:

#import "NSScanner+MyAdditions.h"

@implementation NSScanner (MyAdditions)
  - (BOOL)my_scanCGFloat:(CGFloat *) cgFloatValue {
#if CGFLOAT_IS_DOUBLE
    return [self scanDouble:cgFloatValue];
#else
    return [self scanFloat:cgFloatValue];
#endif
}
@end

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