OC_变量类型

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字符串的替代符为：@，且每个字符串前面都要加@，而且字符串的变量为指针形式

//字符串 对象类型
NSLog(@"hello,world");
NSString * mystring = @"dajiahao";
NSLog(@"myfirst:%@", mystring);

//字符串拼接
NSString * mystring1 = @"hello";
NSString * mystring2 = @"world";
NSString * mystring3 = [NSString stringWithFormat:@"%@ %@",mystring1,mystring2];
NSLog(@"mystring3:%@",mystring3);

//字符串截取
NSString * mystring4 = [mystring3 substringFromIndex:5];
NSLog(@"substring3:%@",mystring4);

//字符串替换
NSString * mystring5 = [mystring3 stringByReplacingOccurrencesOfString:@"world" withString:@"haha"];
NSLog(@"%@", mystring5);

//字符
char mychar = 'c';
NSLog(@"char:%c",mychar);

注意整数的替代符是 %ld

//整数
NSUInteger myint1 = 10;
NSLog(@"myint1:%ld",myint1);

float小数点后7位，double小数点后15位

//小数
CGFloat myfloat = 3.13132123;
double mydouble = 3.13132123;
NSLog(@"myfloat:%f,%f",myfloat,mydouble);

数组不可变数组，长度不能改变，只能存放对象类型的值，例如字符串，不能保存整型这种，需要转换成对象类型才行。

//数组 不能存放inter这种非对象类型，不可改变
NSArray *arr = [[NSArray alloc] initWithObjects:@"a",@"b",@"c", nil];
NSLog(@"%@,%@,%@",arr[0],arr[1],arr[2]);

//可变数组 不能存放inter这种非对象类型，不可改变
NSMutableArray *muarr = [NSMutableArray array];
[muarr addObject:@"a"];//添加
[muarr addObject:@"b"];
[muarr addObject:@"c"];
NSLog(@"%@,%@,%@",muarr[0],muarr[1],muarr[2]);
[muarr removeObject:0];
NSLog(@"%@,%@",muarr[0],muarr[1]);

//字典
NSDictionary *dict = [[NSDictionary alloc] initWithObjectsAndKeys:@"value1",@"key1",@"value2",@"key2", nil];
NSLog(@"%@",[dict objectForKey:@"key1"]);
NSLog(@"%@",[dict objectForKey:@"key2"]);

NSDictionary *dict1 = [[NSDictionary alloc] initWithObjects:@[@"value1",@"value2"] forKeys:@[@"key1",@"key2"]];
NSLog(@"%@",[dict objectForKey:@"key1"]);
NSLog(@"%@",[dict objectForKey:@"key2"]);

//可变字典
NSMutableDictionary *mudict = [[NSMutableDictionary alloc] init];
[mudict setObject:@"value1" forKey:@"key1"];//添加
[mudict setObject:@"value2" forKey:@"key2"];
NSLog(@"%@",[dict objectForKey:@"key1"]);
NSLog(@"%@",[dict objectForKey:@"key2"]);
[mudict removeObjectForKey:@"key2"];//删除

再加个句式，OC和python等一样，循环语句也可以用for in结构

//循环语句
NSArray *arr = [[NSArray alloc] initWithObjects:@"a",@"b",@"c", nil];
for (NSString *value in arr){
NSLog(@"%@", value);
}