这是（用户）micmoo 对类和实例方法有什么区别的回应的后续问题？.
如果我将变量 numberOfPeople 从静态更改为类中的局部变量，我会得到 numberOfPeople 为 0。我还添加了一行来显示 numberOfPeople 变量每次递增后的值。为避免混淆，我的代码如下：
// Diffrentiating between class method and instance method
#import <Foundation/Foundation.h>
// static int numberOfPeople = 0;
@interface MNPerson : NSObject {
int age; //instance variable
int numberOfPeople;
}
+ (int)population; //class method. Returns how many people have been made.
- (id)init; //instance. Constructs object, increments numberOfPeople by one.
- (int)age; //instance. returns the person age
@end
@implementation MNPerson
int numberOfPeople = 0;
- (id)init{
if (self = [super init]){
numberOfPeople++;
NSLog(@"Number of people = %i", numberOfPeople);
age = 0;
}
return self;
}
+ (int)population{
return numberOfPeople;
}
- (int)age{
return age;
}
@end
int main(int argc, const char *argv[])
{
@autoreleasepool {
MNPerson *micmoo = [[MNPerson alloc] init];
MNPerson *jon = [[MNPerson alloc] init];
NSLog(@"Age: %d",[micmoo age]);
NSLog(@"Number Of people: %d",[MNPerson population]);
}
}
输出：
在初始化块中。人数 = 1 在初始化块中。人数 = 1 年龄：0 人数：0
案例 2：如果您将实现中的 numberOfPeople 更改为 5（比如说）。输出仍然没有意义。
预先感谢您的帮助。