ios - 在 NSArray 中排序对象？

Question

我有一个对象，如下图

#import <Foundation/Foundation.h>

@interface CountriesDAO : NSObject

@property (nonatomic, retain) NSString * countryname;

@end



#import "CountriesDAO.h"

@implementation CountriesDAO
@synthesize countryname;

@end

我已将其保存在 appDelegate 中的数组中。

@property (nonatomic, retain) NSArray *countriesArray;

@synthesize countriesArray;

在另一个 Controller 中，我像这样获取它

  NSArray *countriesArray = appDelegate.countriesArray; It works fine and I get array.

当我尝试用这种方式对它进行排序时。

 NSArray *countriesArray1 = appDelegate.countriesArray;
    NSSortDescriptor *valueDescriptor = [[NSSortDescriptor alloc] initWithKey:@"countryname" ascending:YES];
    NSArray * descriptors = [NSArray arrayWithObject:valueDescriptor];

    countriesArray = [countriesArray1 sortedArrayUsingDescriptors:descriptors];

我得到错误

[__NSCFType count]: unrecognized selector sent to instance 0xa83b4d0
2013-11-01 13:21:08.882 ECP[13597:c07] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFType count]: unrecognized selector sent to instance 0xa83b4d0'

这里 countriesArray 定义为

 @property (nonatomic, retain) NSArray *countriesArray;

Answer 1

我是这样做的，它对我有用。

countriesArray = [[NSMutableArray alloc] init];


for (CountriesDAO *info in appDelegate.countriesArray) {
    [countriesArray addObject:info.countryname];
}    

[countriesArray sortUsingSelector:@selector(localizedCaseInsensitiveCompare:)];