NSString関連アクション

    //         
    NSString * str_1 = @"Hello"; //     
    int a = 123;
    NSString * str_2 = [NSString stringWithFormat:@"%d",a];
    
    //             C     OC       
    NSString * str_3 = [NSString stringWithUTF8String:"hello world"];
    NSString * str_4 = [NSString stringWithFormat:@"%s","hello world"];
    
    //     
    NSString* str_5 = @"123";
    int b=[str_5 intValue];//           
    float c=[str_5 floatValue];//       float 
    double d=[str_5 doubleValue];//       double 
    
    //   NSString Message(OC     :typedef unsigned short unichar)
    NSLog(@"%ld",[str_1 length]);//      
    NSLog(@"%c",[str_1 characterAtIndex:1]);//         
    BOOL ret0 =  [str_1 isEqualToString:str_2];//                YES(1)      NO(0)
    long ret1 = [str_1 compare:str_2];//           str1     1     0     -1
    long ret2 = [str_1 caseInsensitiveCompare:str_2];//             
    
    NSString * ptr = [str_1 uppercaseString];//                           
    ptr = [str_1 lowercaseString];//                           
    ptr = [str_3 capitalizedString];//                         
    
    NSString * str_6 = @"hello world";
    NSRange range = [str_6 rangeOfString:@"wr"];//          NSNotFound     location length
    if (range.location != NSNotFound) {
        NSLog(@"%ld %ld",range.location, range.length);
    }
    
    NSString * str_7 = @"helloworld";
    NSString * ptr1 = [str_7 substringToIndex:4];//         0   4    4
    NSString * ptr2 = [str_7 substringFromIndex:5];//   5             5
    NSRange range1 = {4,3};//      
    NSString * ptr3 = [str_7 substringWithRange:range1];// range       
    NSString * ptr4 = [str_7 substringWithRange:NSMakeRange(4,3)];//NSMakeRange         
    
    NSString * str_8 = @"www.1000phone.com";
    BOOL ret = [str_8 hasPrefix:@"www"];//               
    
    NSString * str_9 = @"1.txt";
    BOOL ret4 = [str_9 hasSuffix:@".txt"];//                
    
    //NSMutableString     (        )    NSString    NSString     
    NSMutableString * str_10 = [[NSMutableString alloc]initWithString:@"hello"];//                 
    [str_10 insertString:@"123" atIndex:1];//     (    )    NSString     
    [str_10 appendString:@"123"];//           
    [str_10 deleteCharactersInRange:NSMakeRange(0, 2)];//       length   
    [str_10 setString:@"qianfeng"];//                
    [str_10 replaceCharactersInRange:NSMakeRange(3, 1) withString:@"ios"];//        length