每日一练：OC中的对象概念1

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[]) {

    @autoreleasepool {

        // insert code here...

        NSDate *now = [NSDate date];

        //时间指针格式

        NSLog(@"The time for now is :%p. \n", now);

        //时间数据格式

        NSLog(@"The time for now is %@ \n", now);

        //计算1970年1月1日 12点中到现在的时间

        double seconds = [now timeIntervalSince1970];

        

        NSLog(@"From 1970-01-01 12:00 to now is :%f seconds\n", seconds);

        

    }

    return 0;

}

Result：

2018-03-10 14:15:08.101631+0800 TOCNSDatea[37619:12858536] The time for now is :0x10045f2c0.

2018-03-10 14:15:08.101949+0800 TOCNSDatea[37619:12858536] The time for now is Sat Mar 10 14:15:08 2018

2018-03-10 14:15:08.101967+0800 TOCNSDatea[37619:12858536] From 1970-01-01 12:00 to now is :1520662508.101608 seconds

Program ended with exit code: 0