obj-c中NSString的常用方法

#import <Foundation/Foundation.h> /** NSString中常用的类方法 + (nullable instancetype)stringWithUTF8String:(const char *)nullTerminatedCString; instancetypetype 作为返回值 代表返回的是当前这个类的对象 作用：将C语言的字符串转化为OC字符串对象 + (instancetype)stringWithFormat:(NSString *)format, ... NS_FORMAT_FUNCTION(1,2); 作用：拼接一个字符串对象 NSString中常用的对象方法 1). length 方法 返回值 NSUInteger ,得到字符串的字符的个数，可以处理中文 2). characterAtIndex 得到字符串中指定下标的字符 - (unichar)characterAtIndex:(NSUInteger)index; 3). 判断两个字符串是否相等 - (BOOL)isEqualToString:(NSString *)aString; 4). 比较字符串大小 - (NSComparisonResult)compare:(NSString *)string; NSComparisonResult : typedef NS_CLOSED_ENUM(NSInteger, NSComparisonResult) { NSOrderedAscending = -1L, NSOrderedSame, NSOrderedDescending }; */ int main(int argc, const char * argv[]) { @autoreleasepool { NSString *str = @"qwertyuiop"; NSUInteger len = [str length]; NSLog(@"%ld", len); unichar ch = [str characterAtIndex:2]; NSLog(@"ch = %C", ch); NSString *str1 = @"qq"; NSString *str2 = [NSString stringWithFormat:@"qq"]; BOOL b = [str1 isEqualToString:str2]; NSLog(@"%d", b); NSComparisonResult res = [str1 compare:str2]; NSLog(@"%ld", res); } return 0; }