Foundation之NSArray

一、NSArray的使用

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

    @autoreleasepool {
        
        // 创建有多个元素的数组，nil代表数组元素结束
        NSMutableString *s1 = [NSMutableString stringWithString:@"a"];
        NSMutableString *s2 = [NSMutableString stringWithString:@"b"];
        NSMutableString *s3 = [NSMutableString stringWithString:@"c"];
        NSArray *arr1 = [NSArray arrayWithObjects:s1, s2, s3, nil];
        // 获取数组元素个数
        NSLog(@"%zi", [arr1 count]); //3
        // 判断数组中是否包含某个元素
        BOOL r1 = [arr1 containsObject:@"b"];
        NSLog(@"%i", r1); //1
        // 获取最后一个元素
        NSLog(@"%@", [arr1 lastObject]); //c
        // 通过索引获取数组元素
        NSLog(@"%@", [arr1 objectAtIndex:1]); //b
        // 查找元素的索引
        NSLog(@"%zi", [arr1 indexOfObject:@"c"]); //2
        // 让数组中的每个元素都调用setString:方法
        [arr1 makeObjectsPerformSelector:@selector(setString:) withObject:@"d"];
        NSLog(@"%@", arr1); //(d,d,d)
        // 使用for遍历数组
        NSUInteger count = [arr1 count];
        for (int i=0; i<count; i++) {
            NSLog(@"%@", [arr1 objectAtIndex:i]);
        }
        // 使用for in遍历数组
        for (id obj in arr1) {
            NSLog(@"%@", obj);
        }
        // 使用Block遍历数组
        [arr1 enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
            NSLog(@"%zi = %@", idx, obj);
            if (idx==1) *stop = YES; //遍历到第2个元素终止遍历
        }];
        // 通过迭代器遍历数组 正序
        NSEnumerator *et1 = [arr1 objectEnumerator];
        id o1 = nil;
        while (o1 = [et1 nextObject]) {
            NSLog(@"%@", o1);
        }
        // 通过迭代器遍历数组 反序
        NSEnumerator *et2 = [arr1 reverseObjectEnumerator];
        id o2 = nil;
        while (o2 = [et2 nextObject]) {
            NSLog(@"%@", o2);
        }
        
        
        // 派生出新的数组
        NSArray *array1 = [NSArray arrayWithObjects:@"1", @"2", nil];
        NSArray *array2 = [array1 arrayByAddingObject:@"3"];
        NSArray *array3 = [array1 arrayByAddingObjectsFromArray:[NSArray arrayWithObjects:@"4", @"5", nil]];
        NSLog(@"%@", array1); // (1,2)
        NSLog(@"%@", array2); // (1,2,3)
        NSLog(@"%@", array3); // (1,2,4,5)
        NSArray *array4 = [array3 subarrayWithRange:NSMakeRange(1, 2)];
        NSLog(@"%@", array4); // (2,4)
        
        // 利用分隔符将数组元素拼接成一个字符串
        NSString *str = [array3 componentsJoinedByString:@"-"]; //1-2-4-5
        NSLog(@"%@", str);
        
        // 将数组写入文件（xml格式），生成的文件见下图
        [array3 writeToFile:@"/Users/Lane/Desktop/array.xml" atomically:YES];
        // 从文件中读取数组，格式见下图
        NSArray *array5 = [NSArray arrayWithContentsOfFile:@"/Users/Lane/Desktop/array.xml"];
        NSLog(@"%@", array5);
        
        // 通过selector进行数组排序
        NSArray *array6 = [NSArray arrayWithObjects:@"4", @"2", @"5", @"3", nil];
        // 指定元素的比较方法：NSString的compare:方法
        NSArray *array7 = [array6 sortedArrayUsingSelector:@selector(compare:)];
        NSLog(@"%@", array7); // (2,3,4,5)
        // 如果是其他类型，则要自定义比较方法
        // 例如Student有fistName和lastName两个成员变量，则比较方法如下：
        /*
         - (NSComparisonResult)compare:(Student *)otherStudent {
            // 先比较fistName
            NSComparisonResult result = [self.fistName compare:otherStudent.fistName];
            if (result==NSOrderedSame) { // 如果fistName相同，则比较lastName
                result = [self.lastName compare:otherStudent.lastName];
            }
            return result;
         }
        */
        // 通过Block进行数组排序
        NSArray *array8 = [array6 sortedArrayUsingComparator:^NSComparisonResult(NSString *obj1, NSString *obj2) {
            return [obj1 compare:obj2];
        }];
        NSLog(@"%@", array8); // (2,3,4,5)
        // 通过排序描述器进行数组排序
        /*
         NSSortDescriptor *bookNameDesc = [NSSortDescriptor sortDescriptorWithKey:@"book.name" ascending:YES];
         NSSortDescriptor *fistNameDesc = [NSSortDescriptor sortDescriptorWithKey:@"fistName" ascending:YES];
         NSSortDescriptor *lastNameDesc = [NSSortDescriptor sortDescriptorWithKey:@"lastName" ascending:YES];
         // 先按书名排序，再按fistName排序，最后按lastName排序
         [array sortedArrayUsingDescriptors:[NSArray arrayWithObjects:bookNameDesc, fistNameDesc, lastNameDesc, nil]];
        */
        
        // 数组的内存管理
        NSObject *obj1 = [[NSObject alloc] init];
        NSObject *obj2 = [[NSObject alloc] init];
        NSObject *obj3 = [[NSObject alloc] init];
        NSLog(@"obj1.retainCount=%zi", [obj1 retainCount]); //obj1.retainCount=1
        NSLog(@"obj2.retainCount=%zi", [obj2 retainCount]); //obj2.retainCount=1
        NSLog(@"obj3.retainCount=%zi", [obj3 retainCount]); //obj3.retainCount=1
        // 把一个对象加到NSArray时，该对象的引用计数会加1
        NSArray *arr2 = [[NSArray alloc] initWithObjects:obj1, obj2, obj3, nil];
        NSLog(@"obj1.retainCount=%zi", [obj1 retainCount]); //obj1.retainCount=2
        NSLog(@"obj2.retainCount=%zi", [obj2 retainCount]); //obj2.retainCount=2
        NSLog(@"obj3.retainCount=%zi", [obj3 retainCount]); //obj3.retainCount=2
        // 数组被销毁的时候会对所有元素都进行release
        [arr2 release];
        NSLog(@"obj1.retainCount=%zi", [obj1 retainCount]); //obj1.retainCount=1
        NSLog(@"obj2.retainCount=%zi", [obj2 retainCount]); //obj2.retainCount=1
        NSLog(@"obj3.retainCount=%zi", [obj3 retainCount]); //obj3.retainCount=1
        [obj1 release]; [obj2 release]; [obj3 release];
        
        
    
    }
    return 0;
}

NSArray生成的文件：