2.结构体
2.1是程序员自己创建的一种数据类型
2.2语法
2.2.1结构体的创建
2.2.2 使用结构体类型定义变量
2.2.3结构体变量的操作
2.2.3.1初始化：整体进行
2.2.3.2赋值：只能通过点运算符，逐个进行
2.2.3.3访问：只能通过点运算符，逐个进行
2.3字符对齐规则
2.3.1找到结构体中占内存最大的基本数据类型的成员变量
2.3.2以该成员所占字节数为单位，为每个成员变量分配存储空间
2.3.3从第二个成员开始，将待分配的字节编号除以该成员所占的字节数。如果余数不为0，则空出该字节不用；如果余数为0，则将该字节分配给该变量
结构体Size4.png
2.4使用结构体的目的是为了封装细节，简化编程。
struct Example
{
int i;//成员变量
char ch;
double d;
};
typedef struct
{
int I;
char ch;
double d;
}Example1;
typedef struct
{
char ch;
int I;
}Size1;
typedef struct
{
Size1 s;
short int si;
}Size4;
typedef struct
{
char *name;
int age1;
int ID;
char *address;
}Student;
@interface ViewController ()
@property (weak, nonatomic) IBOutlet UILabel *outputLabel;
-(void)method1;//语法
-(void)method2;//字符对齐规则使用结构体的目的
-(void)method3;//使用结构体的目的
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
[self method1];
[self method2];
[self method3];
}
-(void)method1
{
long int a;
a = 10;
self.outputLabel.text = [NSString stringWithFormat:@"%ld",a];
struct Example s;
s.i = 10;//点是成员运算符
s.ch = 'a';//结构体变量s只能逐个成员进行赋值，不能整体赋值
s.d = 3.14;
self.outputLabel.text = [NSString stringWithFormat:@"%d,%c,%g",s.i,s.ch,s.d];//结构体变量s只能逐个成员进行访问，不能整体访问
struct Example s1 = {40,'b',3.14};
self.outputLabel.text = [NSString stringWithFormat:@"%d,%c,%g",s1.i,s1.ch,s1.d];//初始化必须整体进行
Example1 s2 = {50,'c',2.68};
self.outputLabel.text = [NSString stringWithFormat:@"%d,%c,%g",s2.i,s2.ch,s2.d];
}
-(void)method2
{
self.outputLabel.text = [NSString stringWithFormat:@"%lu",sizeof(Size1)];
self.outputLabel.text = [NSString stringWithFormat:@"%lu",sizeof(Size4)];
}
-(void)method3
{
char *name1 = "张三";
int age1 = 18;
int ID1 = 1000;
char *address1 = "江苏南京";
char *name2 = "李四";
int age2 = 20;
int ID2 = 1001;
char *address2 = "广东深圳";
//...
Student stu1 = {"张三",18,1000,"江苏南京"};
}
3.联合
3.1也是程序员创建的一种数据类型
3.2语法
3.3 联合中所有成员变量共用一块儿存储空间，这块空间的大小是最大的成员呢变量的字节数。
#import "ViewController.h"
union U
{
int x;
int y;
int z;
};
typedef union
{
double d;
int I;
}U1;
@interface ViewController ()
@property (weak, nonatomic) IBOutlet UILabel *outputLabel;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
union U u1;
u1.x = 100;
self.outputLabel.text = [NSString stringWithFormat:@"x=%d\ny=%d\nz=%d",u1.x,u1.y,u1.z];
u1.y = 200;
self.outputLabel.text = [NSString stringWithFormat:@"x=%d\ny=%d\nz=%d",u1.x,u1.y,u1.z];
U1 u2={3.14};//初始化时，只能给第一个成员变量赋值
self.outputLabel.text = [NSString stringWithFormat:@"d=%g\ni=%d",u2.d,u2.i];
}
4.枚举
4.1也是程序员创建的一种数据类型
4.2没有成员变量，而是枚举常量
#import "ViewController.h"
enum Week
{
Monday,Tuesday,Wednesday,Thurday,Friday,Saturday,Sunday,
};
@interface ViewController ()
@property (weak, nonatomic) IBOutlet UILabel *outputLabel;
-(NSString *)stringOfWeek:(enum Week)day;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
self.outputLabel.text = [NSString stringWithFormat:@"%d\n%d\n%d\n%d",Monday,Tuesday,Wednesday,Sunday];
self.outputLabel.text = [self stringOfWeek:Wednesday];
}
-(NSString *)stringOfWeek:(enum Week)day
{
switch (day) {
case Monday:
return @"星期一";
break;
case Tuesday:
return @"星期二";
break;
case Wednesday:
return @"星期三";
break;
case Thurday:
return @"星期四";
break;
case Friday:
return @"星期五";
break;
case Saturday:
return @"星期六";
break;
case Sunday:
return @"星期天";
break;
default:
break;
}
}
@end
代码太多了用方法封装
常量太多了用枚举来封装
变量太多了用结构体来封装
练习小球跳转
#import "ViewController.h"
typedef enum
{
LEFTUP,LEFTDOWN,RIGHTUP,RIGHTDOWN,
}Direction;
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
}
- (IBAction)move:(UIButton *)sender {
CGRect rect = sender.frame;
rect.size.width = 100;
rect.size.height = 100;
int screenWidth =[[UIScreen mainScreen]bounds].size.width;
int screenHeight =[[UIScreen mainScreen]bounds].size.height;
int maxWidth = screenWidth - rect.size.width;
int maxHeight = screenHeight - rect.size.height;
static Direction direction = RIGHTDOWN;
switch (direction)
{
case RIGHTDOWN:
rect.origin.x += 10;
rect.origin.y += 10;
if(rect.origin.x > maxWidth)
{
direction = LEFTDOWN;
rect.size.width = screenWidth - rect.origin.x;
}
if(rect.origin.y > maxHeight)
{
direction = RIGHTUP;
}
break;
case LEFTDOWN:
rect.origin.x -= 10;
rect.origin.y += 10;
if(rect.origin.x < 0)
{
direction = RIGHTDOWN;
}
if(rect.origin.y > maxHeight)
{
direction = LEFTUP;
}
break;
case RIGHTUP:
rect.origin.x += 10;
rect.origin.y -= 10;
if(rect.origin.x > maxWidth)
{
direction = LEFTUP;
}
if(rect.origin.y < 0)
{
direction = RIGHTDOWN;
}
break;
case LEFTUP:
rect.origin.x -= 10;
rect.origin.y -= 10;
if(rect.origin.x < 0)
{
direction = RIGHTUP;
}
if (rect.origin.y < 0)
{
direction = LEFTDOWN;
}
break;
default:
break;
}
sender.frame = rect;
}
```
网友评论