ObjectiveC 类型

1. Strings

1) 简单字符串

NSString *aString = @"this is a string";
NSString *anotherString = @"and this is another one";

2) 对象初始化

NSString *aString = [[NSString alloc] initWithString:@"some string literal"];
NSString *aString = [NSString stringWithString:@"some string literal"];

3) 格式化字符串

int theValueOfPi = 3;
//produces the string "pi is exactly 3!"
NSString *aString = [NSString stringWithFormat:@"pi is exactly %d!", theValueOfPi];

4) 对象格式化

NSString *aString = @"criminals";
NSString *anotherString = [NSString stringWithFormat:@"When you %@ strings, only %@ will
use strings.", @"criminalize", aString];

5) 字符串比较

NSString *aString = @"hello";
NSString *anotherString = @"hello";
BOOL stringsAreEqual = ([aString isEqualToString:anotherString]);

BOOL stringsAreEqual = (aString == anotherString); //这是错误的