////  main.m//  OC4_NSString操作////  Created by zhangxueming on 15/6/10.//  Copyright (c) 2015年 zhangxueming. All rights reserved.//#import 
     
      //NSStringint main(int argc, const char * argv[]) {    @autoreleasepool {        NSString *str1 = @"hello world 千锋";        //求字符串长度        NSUInteger len = [str1 length];        NSLog(@"len = %li", len);        //获取字符串指定位置的字符        unichar ch = [str1 characterAtIndex:13];        NSLog(@"ch = %C", ch);//%C打印unichar字符 %c打印ASCII字符                //字符串提取        //从传入下标位置提取子串到字符串结束        NSString *subStr1 = [str1 substringFromIndex:4];        NSLog(@"subStr1 = %@", subStr1);        //提取子串到指定位置(不包含下标位置字符)        NSString *subStr2 = [str1 substringToIndex:7];        NSLog(@"subStr2 = %@",subStr2);                //提取指定范围内的字符串        NSRange range = {
   6,5};        NSString *subStr3 = [str1 substringWithRange:range];        NSLog(@"subStr3 = %@",  subStr3);                //NSMakeRange();//构建NSRange变量        NSString *subStr4 = [str1 substringWithRange:NSMakeRange(2, 6)];        NSLog(@"subStr4 = %@", subStr4);                //字符串比较        NSString *str2 = [NSString stringWithCString:"hallo world中国" encoding:NSUTF8StringEncoding];        NSString *str3 = [NSString stringWithUTF8String:"hello world中国"];        NSComparisonResult result = [str2 compare:str3];        if (result == NSOrderedAscending) {
   //递增            NSLog(@"str2 < str3");        }        else if(result == NSOrderedDescending)//递减        {            NSLog(@"str2 > str3");        }        else        {            NSLog(@"str2 == str3");        }        //以大小写不敏感方式比较字符串        //[str2 caseInsensitiveCompare:str3];        //判断两个字符串是否相等        //- (BOOL)isEqualToString:(NSString *)aString;        BOOL ret = [str2 isEqualTo:str3];        if (ret==YES) {            NSLog(@"str2 == str3");        }        else        {            NSLog(@"str2 != str3");        }        //判断前缀子串        //- (BOOL)hasPrefix:(NSString *)aString;        BOOL ret1 = [@"www.baidu.com" hasPrefix:@"www."];        NSLog(@"ret1 = %d", ret1);        //判断后缀子串        //- (BOOL)hasSuffix:(NSString *)aString;        BOOL ret2 = [@"www.hao123.com" hasSuffix:@"com"];        NSLog(@"ret2 = %d", ret2);        //判断是否包含子串(10.10macos)        BOOL ret3 = [@"hao123" containsString:@"hao"];        NSLog(@"ret3 = %d", ret3);                //查找子串        NSString *str4 = [[NSString alloc] initWithFormat:@"%s","hello world qianworldfeng"];        NSRange range1 =[str4 rangeOfString:@"world"];        if (range1.location == NSNotFound) {
   //不能查找对应的子串, 返回long类型最大值            NSLog(@"没有查找到字串 notfound = %lu", NSNotFound);        }        else        {            NSLog(@"location = %lu length = %lu", range1.location, range1.length);        }                //倒序查找子串        NSRange range2 = [str4 rangeOfString:@"world" options:NSBackwardsSearch];        NSLog(@"location = %li length = %li", range2.location, range2.length);                //字符串追加        //并不是直接在原字符串的末尾追加字符串, 而是利用传入的字符串及原字符串创建一个新的字符串        NSString *str5 = @"hello";        NSLog(@"%p", str5);        str5 = [str5 stringByAppendingString:@"world"];        NSLog(@"str5 = %@", str5);        NSLog(@"%p", str5);                //格式化追加字符串        NSString *str6 = @"qianfeng";        str6 = [str6 stringByAppendingFormat:@"%d%s",123,"helloworld"];        NSLog(@"str6 = %@", str6);                //把字符换串对象转换成整型 浮点型        int a = [@"12345" intValue];        float f = [@"3.14" floatValue];        NSLog(@"a = %d f = %.2f", a, f);                //返回公共前缀子串        NSString *str7 = [@"www.baidu.com" commonPrefixWithString:@"www.hao123.com" options:NSLiteralSearch];        NSLog(@"str7 = %@", str7);                //大小写转换        //把小写字母转换成大写字母        NSString *str8 = [@"baidu中国" uppercaseString];        NSLog(@"str8 = %@", str8);        //把大写字母转换成小写字母        NSString *str9 = [@"BaiDU" lowercaseString];        NSLog(@"str9 = %@", str9);        //把每个单词的首字母大写        NSString *str10= [@"bai du qian feng" capitalizedString];        NSLog(@"str10 = %@", str10);                //字符串替换        //- (NSString *)stringByReplacingOccurrencesOfString:(NSString *)target withString:(NSString *)replacement        NSString *str11= @"hello world qianfeng hello world hello hell qianfeng";        str11 = [str11 stringByReplacingOccurrencesOfString:@"hello" withString:@"welcome"];        NSLog(@"str11 = %@", str11);                //替换指定范围内的字符        //- (NSString *)stringByReplacingCharactersInRange:(NSRange)range withString:(NSString *)replacement        NSString *str12 = @"hello world qianfeng";        str12 = [str12 stringByReplacingCharactersInRange:NSMakeRange(12, 8) withString:@"welcome"];        NSLog(@"str12 = %@", str12);                //把OC的字符串对象转换成C字符串        NSLog(@"%s", [@"hello world" UTF8String]);                //用网址的内容生成OC字符串对像        //- (instancetype)initWithContentsOfURL:(NSURL *)url encoding:(NSStringEncoding)enc error:(NSError **)error;        //+ (instancetype)stringWithContentsOfURL:(NSURL *)url encoding:(NSStringEncoding)enc error:(NSError **)error;        NSURL *url= [[NSURL alloc] initWithString:@"http://www.baidu.com"];        NSString *urlContent = [[NSString alloc] initWithContentsOfURL:url encoding:NSUTF8StringEncoding error:nil];//nil 空指针        NSLog(@"urlContent = %@", urlContent);                //用文件的内容生成字符串        //- (instancetype)initWithContentsOfFile:(NSString *)path encoding:(NSStringEncoding)enc error:(NSError **)error;        //+ (instancetype)stringWithContentsOfFile:(NSString *)path encoding:(NSStringEncoding)enc error:(NSError **)error;        NSString *fileContent = [NSString stringWithContentsOfFile:@"/Users/zhangxueming/Desktop/json.txt" encoding:NSUTF8StringEncoding error:nil];        NSLog(@"fileContent = %@", fileContent);            }    return 0;}