OC字面量语法

要记  ：用字面量语法创建数组和字典的时候 若值为nil会抛出异常 务必保证值中不含nil

NSString *string=@"XXXXXX";

NSNumber *intNumber=@1;

NSNumber *floatNumber=@1.1f;

NSNumber *doubleNumber=@1.211231231;

NSNumber *boolNumber=@YES;

NSNumber *charNumber=@'q';

int x=20;

int y=30;

NSNumber * expressionNumber=@(x*y);

数组字面量

NSArray *animals=[NSArray arrayWithObjects:"dog","cat",nil];

字面量代替的语法

NSArray *animals=@[@"dog",@"cat"];

NSString *dog=animals[1];

字典字面量

NSDictionary *AA=[NSDictionaryWithObjectsAndkeys:@"AA",@"A",@"BB",@"B",[NSNumber numberWithInt:28],@"age",nil];

 这个是<对象><健>  

NSString *lastName=[ AA objectForKey:@"lastName"];

字面量代替的语法

NSDictionary *AA＝@{@"A":@"AA",@"B":@"BB",@"age",@28};  <健><对象>

NSString * lastName=AA[@"lastName"];

可变数组与字典

[mutableArray replaceObjectAtIndex:1 withObject:@"dog"];

[mutableDictionary setObject:@"HSF" forKey:@"lastName"];

字面量代替的语法

mutableArray[1]=@"dog";

mutableDictionary[@"lastName"]=@"HSF";