作者dreambegins ( ′-`)
看板MacDev
标题[问题] 程式码问题 有关NSSet
时间Wed May 1 15:14:19 2019
不好意思直接贴上 上色过程太麻烦可怕了
如果可以麻烦大大也直接复制贴上到编辑器跑结果
我的第二个问题是结果无法理解
#import <Foundation/Foundation.h>
// Create an integer object
#define INTOBJ(v) [NSNumber numberWithInteger: v]
// Add a print method to NSSet with the Printing category
@interface NSSet (Printing)<=====我想问的第一个问题，括号这个是什麽？
-(void) print;
@end
@implementation NSSet (Printing)
-(void) print {
printf ("{ ");
for (NSNumber *element in self)
printf (" %li ", (long) [element integerValue]);
printf ("} \n"); }
@end
int main (int argc, char * argv[]) {
@autoreleasepool {
NSMutableSet *set1 = [NSMutableSet setWithObjects:
INTOBJ(1), INTOBJ(3), INTOBJ(5), INTOBJ(10), nil];
NSSet *set2 = [NSSet setWithObjects:
INTOBJ(-5), INTOBJ(100), INTOBJ(3), INTOBJ(5), nil];
NSSet *set3 = [NSSet setWithObjects: INTOBJ(12), INTOBJ(200), INTOBJ(3), nil];
NSLog(@"set1: ");
[set1 print];<=====我想问的第三个问题
NSLog(@"set2: ");
[set2 print];
// Equality test
if ([set1 isEqualToSet: set2] == YES)
NSLog (@"set1 equals set2");
else
NSLog (@"set1 is not equal to set2");
// Membership test
if ([set1 containsObject: INTOBJ(10)] == YES)
NSLog (@"set1 contains 10");
else
NSLog (@"set1 does not contain 10");
if ([set2 containsObject: INTOBJ(10)] == YES)
NSLog (@"set2 contains 10");
else
NSLog (@"set2 does not contain 10");
// add and remove objects from mutable set set1
[set1 addObject: INTOBJ(4)];
[set1 removeObject: INTOBJ(10)];
NSLog (@"set1 after adding 4 and removing 10: ");
[set1 print];
// get intersection of two sets
[set1 intersectSet: set2];
NSLog (@"set1 intersect set2: ");
[set1 print];
// union of two sets
[set1 unionSet:set3];
NSLog (@"set1 union set3: ");
[set1 print]; <=====我想问的第二个问题
}
return 0;
}
这本书是精通Obj C...作者提供的讨论区已经404 not found了...QQ 所以上来求救
第一个问题：(printing) 的写法是什麽意思？书本上根本就没交代清楚
第二个问题：书上写的结果是
set1 union set3:
{ 12 3 5 200 }
我觉得很奇怪，union的数学意义不是联集吗？为什麽结果不是{ 1 3 4 5 12 200 }？
第三个问题：为什麽印出这些元素的时候没按照顺序啊？本来就随便排序的吗？
以上 麻烦大大 谢谢！
--
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※ 文章网址: https://webptt.com/cn.aspx?n=bbs/MacDev/M.1556694862.A.48B.html
※ 编辑: dreambegins (39.9.168.193), 05/01/2019 15:16:07
1F：推 darktt: 问题一：这是Category的名称，关於它可以220.133.234.121 05/01 15:50
2F：→ darktt: 看这个220.133.234.121 05/01 15:50
4F：推 ID3238: 问题三：集合没有顺序的概念 211.76.47.143 05/01 17:55
5F：→ yuanruo: 2.因为intersectSet後里面剩{3,5} 再联集122.116.161.187 05/02 01:41
6F：→ yuanruo: 就变成{12, 3, 5 ,200}122.116.161.187 05/02 01:41
7F：→ dreambegins: 谢谢三位大大!! 114.44.73.157 05/02 12:21