Category使用实例，格式化时间 - Chinaunix

1.//
2.// NSDateCategory.h
3.// WebGameIphone
4.//
5.// Created by apple on 12-1-9.
6.// Copyright 2012年 __MyCompanyName__. All rights reserved.
7.//
8.
9.#import <Foundation/Foundation.h>
10.
11.@interface NSDate (NSDateCategory)
12.
13.// 根据格式化样式得到时间字符串
14.- (NSString *)stringWithFormat:(NSString*)fmt;
15.
16.// 根据字符串和格式化样式得到时间
17.+ (NSDate *)dateFromString:(NSString*)str withFormat:(NSString*)fmt;
18.
19.// 改变时间字符串格式化样式
20.+ (NSString *)dateStringReplaceFormat:(NSString*)str oldFormat:(NSString*)fmt newFormat:(NSString*)n_fmt;
21.
22.@end
23.
24.@implementation NSDate (NSDateCategory)
25.
26.- (NSString *)stringWithFormat:(NSString *)fmt {
27. static NSDateFormatter *fmtter;
28.
29. if (fmtter == nil) {
30. fmtter = [[NSDateFormatter alloc] init];
31. }
32.
33. if (fmt == nil || [fmt isEqualToString:@""]) {
34. fmt = @"HH:mm:ss";
35. }
36.
37. [fmtter setDateFormat:fmt];
38.
39. return [fmtter stringFromDate:self];
40.}
41.
42.+ (NSDate *)dateFromString:(NSString *)str withFormat:(NSString *)fmt {
43. static NSDateFormatter *fmtter;
44.
45. if (fmtter == nil) {
46. fmtter = [[NSDateFormatter alloc] init];
47. }
48.
49. if (fmt == nil || [fmt isEqualToString:@""]) {
50. fmt = @"HH:mm:ss";
51. }
52.
53. [fmtter setDateFormat:fmt];
54.
55. return [fmtter dateFromString:str];
56.}
57.
58.+ (NSString *)dateStringReplaceFormat:(NSString*)str oldFormat:(NSString*)fmt newFormat:(NSString*)n_fmt {
59. NSDate *n_date = [NSDate dateFromString:str withFormat:fmt];
60. return [n_date stringWithFormat:n_fmt];
61.}
62.
63.@end

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