QF——OC字符串

        //通过对象方法（动态方法）
        NSString * str1 = [[NSString alloc]initWithUTF8String:"wang1"];
        NSString * str2 = [[NSString alloc]initWithString:@"wang2"];

        //通过类方法（静态方法）
        NSString * str3 = [NSString stringWithUTF8String:"wang3"];
        NSString *str4  =[NSString stringWithString:"wang4"];

//
//  main.m
//  NSStringTest
//
//  Created by mac on 15-2-25.
//  Copyright (c) 2015年 mac. All rights reserved.
//

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[])
{

    @autoreleasepool {
        
        NSString *str = @"wang1.avi";
        
        //根据索引获取字符串元素
        UniChar ch = [str characterAtIndex:0];
        NSLog(@"%c",ch);
        
        //字符串内容比较
        BOOL tag = [str isEqualToString:@"wang1.mp4"];
        NSLog(@"%i",tag);
        if (tag==NO)
        {
            NSLog(@"butong");
        }else
        {
            NSLog(@"xiangtong");
        }
        
        //字符串大小比较
        NSComparisonResult ret = [str compare:@"wang2.avi"];
        if(ret==NSOrderedAscending) //wang1.avi到wang2.avi是增序的
        {
            NSLog(@"up");
        }else if(ret==NSOrderedDescending)
        {
            NSLog(@"down");
        }else
        {
            NSLog(@"equal");
        }
        
        //查找子串的范围range（位置，长度）
        NSRange range = [str rangeOfString:@"wang1"];
        NSLog(@"%lu,%lu",range.location,range.length);
        
        //判断前后缀
        BOOL tag1 = [str hasPrefix:@"wang"];
        if (tag1==YES)
        {
            NSLog(@"是以wang为前缀");
        }
       
        BOOL tag2 = [str hasSuffix:@"avi"];
        if (tag2==YES)
        {
            NSLog(@"是以avi为后缀");
        }
        
        
        //数组串转换成数字
        NSString *intStr = @"1031";
        NSString *floatStr = @"3.14";
        int intNum = [intStr intValue];
        float floatNum = [floatStr floatValue];
        NSLog(@"_____________%f",intNum+floatNum);
        NSLog(@"%i,%f",intNum,floatNum);
        
        
        //大小写转换
        NSString *upperStr = [str uppercaseString];   //把wang1.avi转为大写WANG1.AVI
        NSString *lowerStr = [upperStr lowercaseString];  //再把WANG1.AVI转为wang1.avi
    
        //字符串提取（获取子串）
        NSString *subStr1 = [str substringFromIndex:5];  //从索引5开始到结尾
        NSLog(@"%@",subStr1);
        
        NSString *subStr2 = [str substringToIndex:4];  //从开头到索引4
//        NSRange range1;
//        range1.location = 5;
//        range1.length = 4;
        NSRange range1 = NSMakeRange(5, 4);   //注意：从格式就可以看出，NSMakeRange(5,4)并不是方法，它只是宏替换。
        NSString *subStr3 = [str substringWithRange:range1];
        NSLog(@"%@__%@",subStr2,subStr3);

        
    }
    
    return 0;
}

//
//  main.m
//  NSMutableString
//
//  Created by mac on 15-2-26.
//  Copyright (c) 2015年 mac. All rights reserved.
//

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[])
{

    @autoreleasepool {
        
        //NSMutableString字符串不能这样创建
//        NSMutableString * mutStr = @"wanger";
//        NSMutableString * mutStr = [[NSMutableString alloc]initWithUTF8String:"wanger"];
        
        NSMutableString * mutStr = [NSMutableString stringWithString:@"wang"];
        NSString *str = [NSString stringWithUTF8String:".avi"];
        
        //增（拼接）
        [mutStr appendString:@".avi"];
//        [mutStr appendFormat:@"%@",str];
        [mutStr insertString:@"er" atIndex:4];
        NSLog(@"%@",mutStr);
        
        //删
        NSRange range1 = NSMakeRange(2, 3);
        [mutStr deleteCharactersInRange:range1];
        
        //改
        [mutStr setString:@"wangyawen.avi"]; //重置可变字符串内存中的内容
        
        //替换
        NSRange range2 = NSMakeRange(10, 3);
        [mutStr replaceCharactersInRange:range2 withString:@"mp4"];  //替换
        
        NSLog(@"%@",mutStr);
        
    }
    return 0;
}