ios逻辑运算、三目运算符、赋值运算符、switch语句、for循环

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程序对齐：ctrl+I

ios 想5分钟，想不出来就不想了
1.逻辑运算
1.1 &&：全真为真，有假即假

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    //与 &&
    int a = 3;
    int b = 4;
    int result = a && b;
    self.outputLabel.text = [NSString stringWithFormat:@"%d",result];
    a = 0;
    result = a && b;
    self.outputLabel.text = [NSString stringWithFormat:@"%d",result];
    //判断一个数X是否在数域（3,8]之间
    //3 < x <=8
    int x = 10;
    result = x > 3 && x <= 8;
    self.outputLabel.text = [NSString stringWithFormat:@"%d",result];
    
}

1.2 || : 有真即真，全假为假
1.3 ! : 颠倒黑白
上面三个“非”得运算符最高，其次是“与”最后是“或”

1.4 短路：是编译器对源代码进行的一种优化（删除）

    //短路
    a = 3;
    b = 4;
    int c = 5;
    result = a > b && b < ++c;
    //c = c + 1;
    //result = a > b && b < c;
    self.outputLabel.text = [NSString stringWithFormat:@"%d",c];
  //运行结果c 为5而非6，出现短路情况
  //result = a < b && b < c || c < a遇到类似的式子先确定优先级

练习一输入一个年份值，判断是否为闰年（优化程序）

- (IBAction)juage:(UIButton *)sender {
    int year = [self.inputTextField.text intValue];

    if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0)

    {
        self.outputLabel.text = [NSString stringWithFormat:@"%d是闰年",year];
    }
    else
    {
        self.outputLabel.text = [NSString stringWithFormat:@"%d是平年",year];
    }
}

练习二输入一个年月份值，判读该年该月天数

- (IBAction)calculation:(UIButton *)sender {
    int year = [self.inputYearTextField.text intValue];
    int month = [self.inputMonthTextField.text intValue];
    if (month < 1 || month > 12)
    {
        self.inputMonthTextField.text = @"×";
    }
    int days = 31;
    if (month == 2)
    {
        days = 28 + ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0);
    }
   else if (month == 4 || month == 6 || month == 9 || month == 11)
    {
        days = 30;
    }
   
    self.outputLabel.text = [NSString stringWithFormat:@"%d",days];
    
    
}

2.三目运算符(目表示涉及的表达式的个数)
a++;单目运算符
a+b;双目运算符
max = a > b ? a : b;三目运算符//如果a > b为真则运算第二个表达式a而把第三个表达式直接删除;如果a > b为假则运算第三个表达式b而把第二个表达式直接删除

三目运算练习某年2月有多少天.png

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    int a = 10;
    int b = 20;
    int max;
//    if (a > b)
//    {
//        max = a;
//    }
//    else
//    {
//        max = b;
//    }
    max = a > b ? a : b;
    self.outputLabel.text = [NSString stringWithFormat:@"%d",max];
    //%@表示字符串所占的占位符
    BOOL c = YES;
    self.outputLabel.text = [NSString stringWithFormat:@"%@", c ? @"YES" : @"NO"];
    BOOL isMan = NO;
    //赋值为真时，“三目运算”运算第二个表达式，当为“假”时，则运算第三个表达式；有了三目运算后，逻辑值就不能输出1或0了
    self.outputLabel.text = [NSString stringWithFormat:@"%@",isMan ? @"男" : @"女"];
    self.outputLabel.text = @"请输入一个年份：";
}

- (IBAction)clickButton:(UIButton *)sender {
    int year = [self.inputTextField.text intValue];
    self.outputLabel.text = [NSString stringWithFormat:@"%d年的2月有%d天",
                             year,((year % 4 == 0 && year % 100 != 0 )|| year % 400 == 0) ? 29 : 28];

3.赋值运算符
3.1左值：赋值号左边的值。常量与表达式不能做左值
3.2右结合性(赋值运算是右结合性)
3.3赋值号“=”与逻辑等“==”的区别
3.4复合赋值运算符，注意：其优先级极低

    int x;
    x = 3;//变量x就是一个左值
    //3 = x;//左值不能是常量
   //x + 5 = 10;//左值也不能是表达式
    int y;
    y = x + (y = 10);
    //赋值号“=”与逻辑等“==”的区别
    int a = 10;
    int b = 20;
    self.outputLabel.text = [NSString stringWithFormat:@"%d\n%d",a == b, a = b];
    //a == b 为逻辑运算只有真跟假即输出的值为1或0；而a = b 得到值取决于赋值号右边的b值，原因是因为右结合性故a得到20
    //复合赋值运算符
    x = 10;
    x += 5;//x = x + 5
    self.outputLabel.text = [NSString stringWithFormat:@"%d",x];
    x -= 5;//x = x - 5
    self.outputLabel.text = [NSString stringWithFormat:@"%d",x];
    x *= 5 + 3;//x = x * (5 + 3)
    self.outputLabel.text = [NSString stringWithFormat:@"%d",x];

4.switch语句
4.1表达式的值必须是整数
4.2case后面必须是整数常量，不能重复。但无顺序要求
4.3break语句用于终止switch语句的运行
4.4default用于表达式的值与所有case后面的值均不相同的时，执行其后的语句。可有可无。

@interface ViewController ()
@property (weak, nonatomic) IBOutlet UILabel *outputLabel;
@property (weak, nonatomic) IBOutlet UITextField *intputTextField;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    self.outputLabel.text = @"请输入一个1~7之间的整数";
}
- (IBAction)clickButton:(UIButton *)sender {
    int number = [self.intputTextField.text intValue];
    switch (number)//表达式的值必须是整数，不能是浮点数
    {
        case 1://case后面有且仅有一个整数常量
            self.outputLabel.text = @"星期一";
            break;
        case 2://case后面不能是变量，表达式，浮点数，字符串
            self.outputLabel.text = @"星期二";
            break;
        case 3://case后面不能重复，但无顺序要求
            self.outputLabel.text = @"星期三";
            break;
        case 4:
            self.outputLabel.text = @"星期四";
            break;//终止switch语句的运行
        case 5:
            self.outputLabel.text = @"星期五";
            break;
        case 6:
            self.outputLabel.text = @"星期六";
            break;
        case 7:
            self.outputLabel.text = @"星期日";
            break;
            
        default://所有case后面的值均与number值不相同时，则执行其后的语句。可有可无的
            self.outputLabel.text = @"输入错误";
            break;
    }
}

练习

@interface ViewController ()
@property (weak, nonatomic) IBOutlet UILabel *outputLabel;
@property (weak, nonatomic) IBOutlet UITextField *intputTextField;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    self.outputLabel.text = @"请输入一个字符";
}
- (IBAction)clickButton:(UIButton *)sender {    self.outputLabel.text = @"";
    char ch = [self.intputTextField.text characterAtIndex:0];
    switch (ch) {
        case '0':
            self.outputLabel.text = @"x == 0";
            break;
        case '1':
            self.outputLabel.text = @"x == 1";
            break;
        case '2':
            self.outputLabel.text = @"x == 2";
            break;
        case 'A':
            self.outputLabel.text = @"x == A";
            break;
        case '#':
            self.outputLabel.text = @"x == #";
            break;
    }
}

练习二输入一个年月份值，判读该年该月天数

@interface ViewController ()
@property (weak, nonatomic) IBOutlet UITextField *inputYearTextField;
@property (weak, nonatomic) IBOutlet UITextField *inputMonthTextField;
@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.
}
- (IBAction)clickButton:(UIButton *)sender
{
    int year = [self.inputYearTextField.text intValue];
    int month = [self.inputMonthTextField.text intValue];
    int days = 31;
    switch (month) {
        case 2:
            days = 28 + ((year % 4 == 0 && year % 100 !=0) || year % 400 ==0);
            break;
        case 4:case 6:case 9:case 11:
            days = 30;
            break;
        default:
            break;
    }
    self.outputLabel.text = [NSString stringWithFormat:@"%d",days];
}

5循环
5.1是指依照指定的条件，反复执行某段儿代码
5.2 for

for流程图.png

 NSString *str = @"";
    for (int i = 0; i < 10 ; I++)
    {
        str = [str stringByAppendingFormat:@"%d ",I];
    }
    self.outputLabel.text = str;

求0到100得和

self.outputLabel.text = str;
    int sum = 0;
    for (int i = 1; i <= 100; I++)
    {
        sum += I;
    }
    self.outputLabel.text = [NSString stringWithFormat:@"sum = %d",sum];

练习百分制成绩转换等级成绩

- (IBAction)transfer:(UIButton *)sender {
 self.outputLabel.text = @"";
    int score = [self.inputTextField.text intValue];
    switch (score) {
        case 90 ... 100:
            self.outputLabel.text = @"优";
            break;
        case 60 ... 89:
            self.outputLabel.text = @"一般";
            break;
        case 0 ... 59:
            self.outputLabel.text = @"不及格";
            break;
        default:
            self.inputTextField.text = @"×";
            break;
    }
    
}

练习二求任意两个数之间的和,如[13,28]

- (IBAction)calculation:(UIButton *)sender {
    int firstNumber = [self.inputFirstNumberTextField.text intValue];
    int secondNumber = [self.inputSecondNumberTextField.text intValue];
    if(firstNumber > secondNumber)
    {
        int temp = firstNumber;
        firstNumber = secondNumber;
        secondNumber = temp;
    }
    int sum = 0;
    for (int i = firstNumber; i<=secondNumber; I++)
    {
        sum += I;
    }
    self.outputLabel.text = [NSString stringWithFormat:@"%d",sum];
}

任意两个数之间的和的屏幕显示.png

练习三.png

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    double sum1 = 0;
    double sum2 = 0;
    for (int i = 1; i < 2000000000; i += 4)
    {
        sum1 += 1.0 / I;
        sum2 += 1.0 / (i + 2);
    }
    self.outputLabel.text = [NSString stringWithFormat:@"π=%.15f",4*(sum1 - sum2)];
}

求π的思路.png

循环结构
5for(续)
5.2.1三个表达式的特殊用法
5.2.1.1三个表达式可以分别或同时为空
5.2.1.2三个表达式可以是逗号表达式

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    [self method1];
}
-(void)method1
{
    NSString *str = @"";
    int i = 0;
    for (; i < 10; i++)//表达式一可以为空
    {
        str = [str stringByAppendingFormat:@"%d ",I];
    }
    str = [str stringByAppendingFormat:@"%d ",I];
    self.outputLabel.text = str;
    //死循环
//    str = @"";
//    for (int i = 0; YES; i++)//表达式二可以为空
//    {
//        str = [str stringByAppendingFormat:@"%d ",I];
//        NSLog(@"%d ",i);
//    }
//    self.outputLabel.text = str;
    for (int i = 0; i < 10; )//表达式三可以为空
    {
        NSLog(@"%d",i++);
    }
//    for(; ;)//三个表达式可以同时为空
//    {
//
//    }
}
str = @"";
    for (int i = 0, j = 0, k = 0;i * j * k < 30; i++, j += 2, k++)
    {
        str = [str stringByAppendingFormat:@"i=%d,j=%d,k=%d\n",i,j,k];
    }
    self.outputLabel.text = str;
}

5.3while循环：用于不固定次数的循环

While流程图.png

做练习：删除字符串中除数字、小数点外的其他字符

- (IBAction)clickButton:(UIButton *)sender {
    NSString *str = @"";
    int index = 0;
    while (index < self.inputTextField.text.length)
    {
        char ch = [self.inputTextField.text characterAtIndex:index];
        if((ch >='0' && ch <= '9')||ch == '.')
        {
            str = [str stringByAppendingFormat:@"%c",ch];
        }
        self.outputLabel.text = str;
        index++;
    }    
}

输入任意字符串提取字符串中数字的屏幕显示.png

练习二：将字符串中所有的字符，按大小字母数字或其他字符分类显示

- (IBAction)transfer:(UIButton *)sender {
    NSString *upper = @"";
    NSString *lower = @"";
    NSString *digit = @"";
    NSString *other = @"";
    int index = 0;
    while (index < self.inputTextField.text.length)
    {
        char ch = [self.inputTextField.text characterAtIndex:index];
        switch (ch) {
            case 'A' ... 'Z':
                upper = [upper stringByAppendingFormat:@"%c",ch];
                break;
            case 'a' ... 'z':
                lower = [lower stringByAppendingFormat:@"%c",ch];
                break;
            case '0' ... '9':
                digit = [lower stringByAppendingFormat:@"%c",ch];
                break;
                
            default:
                other = [other stringByAppendingFormat:@"%c",ch];
                break;
        }
        index++;
    }
    self.outputUpperLabel.text = upper;
    self.outputLowerLabel.text = lower;
    self.outputDigitLabel.text = digit;
    self.outputOtherLabel.text = other;
}

将字符串中所有的字符，按大小字母数字或其他字符分类显示屏幕显示.png

5.4do~while循环

-(void)method3
{
    NSString *str = @"";
    int x = 0;
    do
    {
        str = [ str stringByAppendingFormat:@"%d ",x];
        x++;
    }
    while (x < 10);
    self.outputLabel.text = str;
}

do-while流程图.png

做练习将字符串中的小写字母转换成大写字母

- (IBAction)transfer:(UIButton *)sender {
    NSString *str = @"";
    int index = 0;
    do
    {
        char ch = [self.inputTextField.text characterAtIndex:index];
        if (ch >= 'a' && ch <= 'z')
        {
            ch -= 32;
        }
        str = [str stringByAppendingFormat:@"%c",ch];
        index++;
    }while (index < self.inputTextField.text.length);
    self.outputLabel.text = str;
}

练习二统计字符串中大、小写字母、数字、其他字符的个数

- (IBAction)statistics:(UIButton *)sender {
    int upper = 0;
    int lower = 0;
    int digit = 0;
    int other = 0;
    int index = 0;
    do
    {
        char ch = [self.inputTextField.text characterAtIndex:index];
        switch (ch) {
            case 'A' ... 'Z':
                upper++;
                break;
            case 'a' ... 'z':
                lower++;
                break;
            case '0' ... '9':
                digit++;
                break;
            default:
                other++;
                break;
        }
        index++;
    }while (index 

练习、计算器

- (IBAction)clickKey:(UIButton *)sender {
    NSString *str = self.outputLabel.text;
    switch (sender.tag) {
        case 0 ... 9:
            str = [str stringByAppendingFormat:@"%ld",sender.tag];
            break;
        case 10:
            str = [str stringByAppendingFormat:@"+"];
            break;
        case 11:
            str = [str stringByAppendingFormat:@"-"];
            break;
        case 12:
            str = [str stringByAppendingFormat:@"*"];
            break;
        case 13:
            str = [str stringByAppendingFormat:@"/"];
            break;
        case 14:
        {
            int num1 = 0;
            int i = 0;
            for (;[str characterAtIndex:i] >= '0' && [str characterAtIndex:i] <= '9';I++)
            {
                num1 = num1 * 10 + [str characterAtIndex:i] - '0';
            }
            char operator = [str characterAtIndex:i];
            int num2 = 0;
            for (++i;i< str.length && [str characterAtIndex:i] >= '0' && [str characterAtIndex:i] <= '9';I++)
            {
                num2 = num2 * 10 + [str characterAtIndex:i] - '0';
            }
            switch (operator) {
                case '+':
                    str = [NSString stringWithFormat:@"%d",num1 + num2];
                    break;
                case '-':
                    str = [NSString stringWithFormat:@"%d",num1 - num2];
                    break;
                case '*':
                    str = [NSString stringWithFormat:@"%d",num1 * num2];
                    break;
                case '/':
                    str = [NSString stringWithFormat:@"%d",num1 / num2];
                    break;
            }
            break;
        }
            case 15:
            str = @"0";
            break;
    }
    self.outputLabel.text = str;
}

计算器屏幕显示.png

6循环（续）
6.1循环辅助语句
6.1.1 break

-(void)method1
{
    NSString *str = @"";
    for(int i = 0; i < 10; I++)
    {
        str = [str stringByAppendingFormat:@"%d ",I];
        if (i == 5)
        {
            break;
        }
    }
    
    self.outputLabel.text = str;

break流程图.png

6.1.2continue

continue流程图.png

-(void)method2
{
    NSString *str = @"";
    for (int i = 0; i < 10; I++)
    {
        if (i == 5)
        {
            continue;
        }
        str = [str stringByAppendingFormat:@"%d ",I];
    }
    self.outputLabel.text = str;
}

-(void)method2
{
    NSString *str = @"";
for (int i = 1;i <= 5;i++)
    {
        if (i % 2)
        {
            str = [str stringByAppendingFormat:@"*"];
        }
        else
           {
               continue;
           }
        str = [str stringByAppendingFormat:@"#"];
    }
    str = [str stringByAppendingFormat:@"$"];
    self.outputLabel.text = str;
}

做练习：数七的游戏（不含含七和七的倍数），求第30个人数的数是多少？

NSString *str = @"";
    int numberNumbered = 0;
    int personNumber = 0;
    while (1)
    {
        numberNumbered++;
        if (numberNumbered % 7 == 0 || numberNumbered % 10 == 7 || numberNumbered / 10 == 7)
        {
            continue;
        }
        if (++personNumber == 30)
        {
            break;
        }
    }
    self.outputLabel.text = [NSString stringWithFormat:@"第%d个人数的数是%d",personNumber,numberNumbered];