OC之【NSArray使用】

#import <Foundation/Foundation.h>
#import "Student.h"
 
创建一个数组
void
    // 创建一个空的数组
NSArray *array = [NSArray array];
     
    // 创建有1个元素的数组
NSArray arrayWithObject:@"123"];
     
    // 创建有多个元素的数组
NSArray arrayWithObjects:@"a", @"b", @"c", nil];
     
int count = [array  count];
    // count = array.count;
NSLog(@"%i", count);
}
 
数组的简单使用
void
NSObject *obj = [[NSObject alloc] init];
NSArray *array = [NSArray arrayWithObjects:@"a", @"b", @"c" , obj, nil];
    // 判断是否包含了某个元素
if ([array containsObject:@"a"]) {
NSLog(@"包含了字符串a");
    }
     
NSString *last = [array  lastObject];
NSLog(@"last=%@", last);
     
NSString *str = [array  objectAtIndex:1];
NSLog(@"%@", str);
     
int index = [array  indexOfObject:@"c"];
NSLog(@"index=%i", index);
     
release];
}
 
数组的内存管理
void
// 1
Student *stu1 = [[Student alloc] init];
Student *stu2 = [[Student alloc] init];
Student *stu3 = [[Student alloc] init];
     
NSLog(@"stu1:%zi", [stu1 retainCount]);
     
    // 当把一个对象塞进数组中时，这个对象的计数器会加1，也就是说数组会对它做一次retain操作
// 2
NSArray *array = [[NSArray alloc] initWithObjects:stu1, stu2, stu3, nil];
     
NSLog(@"stu1:%zi", [stu1 retainCount]);
     
NSLog(@"count=%zi", array.count);
     
// 1
release];
release];
release];
     
    // 数组被销毁的时候，会对内部的所有元素都做一次release操作
// 0
release];
}
 
给数组里面的元素发送消息
void
Student *stu1 = [Student student];
Student *stu2 = [Student student];
Student *stu3 = [Student student];
     
NSArray *array = [NSArray arrayWithObjects:stu1, stu2, stu3,  nil];
    // 让数组里面的所有对象都调用test方法
    // [array makeObjectsPerformSelector:@selector(test)];
    [array makeObjectsPerformSelector:@selector(test2:) withObject:@"123"];
}
 
遍历数组1
void
Student *stu1 = [Student student];
NSArray *array = [NSArray arrayWithObjects:stu1,  @"1", @"2",  @"3", nil];
int count = array.count;
for (int i = 0; i<count; i++) {
        // id == void *
id obj = [array objectAtIndex:i];
NSLog(@"%i-%@", i, obj);
    }
}
 
遍历数组2
void
Student *stu1 = [Student student];
NSArray *array = [NSArray arrayWithObjects:stu1,  @"1", @"2",  @"3", nil];
    //  快速遍历
int i =0;
for (id obj in
NSLog(@"%i-%@", i, obj);
        i++;
    }
}
 
遍历数组3
void
Student *stu1 = [Student student];
NSArray *array = [NSArray arrayWithObjects:stu1,  @"1", @"2",  @"3", nil];
    [array enumerateObjectsUsingBlock:
id obj, NSUInteger idx, BOOL
NSLog(@"%i-%@", idx, obj);
          
         //  如果索引为1，就停止遍历
if (idx == 1) {
             //  利用指针修改外面BOOL变量的值
YES;
         }
    }];
}
 
遍历数组4
void
Student *stu1 = [Student student];
NSArray *array = [NSArray arrayWithObjects:stu1,  @"1", @"2",  @"3", nil];
     
    // 获取数组的迭代器
    // NSEnumerator *enumerator = [array objectEnumerator];
    // 反序迭代器（从尾部开始遍历元素）
NSEnumerator *enumerator = [array  reverseObjectEnumerator];
     
    // allObjects是取出没有被遍历过的对象
NSArray *array2 = [enumerator  allObjects];
NSLog(@"array2:%@", array2);
     
    // 获取下一个需要遍历的元素
id obj = nil;
while (obj = [enumerator  nextObject]) {
NSLog(@"obj=%@", obj);
    }
}
 
int main(int argc, const char
{
 
    @autoreleasepool {
arrayFor4();
    }
return 0;
}