计算本周是几号到几号

这里写的是给一个日期计算出 这个日期所在的一周是几号到几号。吧日期换成今天日期也就是本周是几号到几号。考虑到有跨月，跨年等等的问题，直接就根据秒数来计算比较不会错。在者考虑到过内外的一周是不同的。国内周一是一周的第一天也就是一周是周一到周日，国外是周日的一周的第一天也就是周日到下周的周六。

#import "ViewController.h"

@interface ViewController ()
{
    UITextField * _textField;
}

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // 2016.8.8 星期一
    // 2016.8.9 星期二
    // 2016.8.11 星期4
    // 2016.8.14 星期日
    UIButton * btn = [[UIButton alloc]initWithFrame:CGRectMake((self.view.frame.size.width-80)/2.0, 100, 80, 30)];
    btn.backgroundColor = [UIColor orangeColor];
    btn.tag = 1001;
    [btn setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
    [btn setTitle:@"国内计算" forState:UIControlStateNormal];
    [btn addTarget:self action:@selector(btnAction:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:btn];
    
    UIButton * btn2 = [[UIButton alloc]initWithFrame:CGRectMake((self.view.frame.size.width-80)/2.0, 140, 80, 30)];
    btn2.backgroundColor = [UIColor orangeColor];
    [btn2 setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
    [btn2 setTitle:@"国外计算" forState:UIControlStateNormal];
    btn2.tag = 1000;
    [btn2 addTarget:self action:@selector(btnAction:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:btn2];
    
    _textField = [[UITextField alloc]initWithFrame:CGRectMake((self.view.frame.size.width-150)/2.0, CGRectGetMinY(btn.frame)-50, 150, 30)];
    _textField.backgroundColor = [UIColor yellowColor];
    [self.view addSubview:_textField];
    
}

- (void)btnAction:(UIButton*)sender
{
    if (sender.tag == 1000) {
        NSDictionary * dic = [ViewController weekfirstAndLastDay:_textField.text Formater:@"yyyy.MM.dd" Foreign:YES];
        NSLog(@"%@",dic);
    }else{
        NSDictionary * dic = [ViewController weekfirstAndLastDay:_textField.text Formater:@"yyyy.MM.dd" Foreign:NO];
        NSLog(@"%@",dic);
    }
}

+(NSDictionary *)weekfirstAndLastDay:(NSString*)dateStr Formater:(NSString*)formater Foreign:(BOOL)foreign
{
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setDateFormat:formater];
   NSDate * date =[formatter dateFromString:dateStr];
   
    NSArray * foreginDateArr = @[@"星期日",@"星期一",@"星期二",@"星期三",@"星期四",@"星期五",@"星期六"];
    NSArray * chineseDateArr = @[@"星期一",@"星期二",@"星期三",@"星期四",@"星期五",@"星期六",@"星期日"];

    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setDateFormat:@"YYYY.MM.dd"];
    NSCalendar *calendar = [NSCalendar currentCalendar];
    NSDateComponents *comp = [calendar components:kCFCalendarUnitYear|kCFCalendarUnitMonth|kCFCalendarUnitDay|kCFCalendarUnitWeekday|kCFCalendarUnitDay fromDate:date];
    NSInteger foreginWeekDay = [comp weekday];
    NSString * foreginDateStr = foreginDateArr[foreginWeekDay-1];
    
    NSInteger chineseWeekDay = 0;
    if (foreign) {
        chineseWeekDay = foreginWeekDay;
    }else{
        for (int i = 0; i < foreginDateArr.count; i++) {
            if ([foreginDateStr isEqualToString:chineseDateArr[i]]) {
                chineseWeekDay = i+1;
                break;
            }
        }
    }
    
    NSInteger gapDate = 7- chineseWeekDay;
    //把时间转化成秒
    NSTimeInterval dateStamp = [date timeIntervalSince1970];
    //把秒转化成时间
    NSTimeInterval beginStamp = dateStamp - 24*60*60*(chineseWeekDay-1);
    NSTimeInterval endStamp = dateStamp + 24*60*60*gapDate;
    NSDate * begin = [NSDate dateWithTimeIntervalSince1970:beginStamp];
    NSDate * end = [NSDate dateWithTimeIntervalSince1970:endStamp];
    NSString * beginStr = [dateFormatter stringFromDate:begin];
    NSString * endStr = [dateFormatter stringFromDate:end];
    NSDictionary * dic = @{@"begin":beginStr,
                           @"end":endStr,
                           @"now":dateStr};
    return dic;
}

思路就是算出这个日期是属于一周的第几天，而后在相应的减去秒数，加上秒数算出一周是从几号到几号。

分别计算了国内外