OC之NSString、NSMutableString学习笔记 常用方法

NSString篇:

1.字符串连接

        NSString *beijing = @"北京";
        NSString *welcome = [beijing stringByAppendingString:@"  欢迎你 "];//字符串连接
        NSLog(@"%@",welcome);

  //两种效果相同的字符串连接    
  NSString *str22 = [str20 stringByAppendingFormat:@"%@",str21];
  NSString *str23 = [str20 stringByAppendingString:str21];

2.字符串长度

NSLog(@"%zi",welcome.length);//字符串的长度

3.字符串比较

注意比较的是内容，此处并未比较地址

        BOOL flag = [beijing isEqualToString:@"北京"];//字符串比较
        NSLog(@"%d",flag);//布尔类型  1相等  0不相等

比较(地址+内容)

        NSString *sstring1 = [[NSString alloc] initWithFormat:@"123"];
        NSString *sstring2 = [[NSString alloc] initWithFormat:@"123"];
        if(sstring1 != sstring2)
            NSLog(@"地址不相等");
        else NSLog(@"地址相等");

          NSLog(@"%p,%p"sstring1,sstring2);

4.字符串向数据的转换

        NSString *number = @"123456",*floatNumber = @"1233.45";
        float aa = [floatNumber floatValue];// 字符串转换成浮点型
        int  a = [number intValue];//字符串转换成整型
        NSLog(@"%d,%f",a,aa);

5.字符串本身元素的索引

        NSString *seachStr = @"12345.doc";
        BOOL f =  [seachStr hasPrefix:@"123"];//判断A字符串是否以B字符串为开头
        BOOL f1 = [seachStr hasSuffix:@".doc"];//判断A字符串是否以B字符串结尾
        NSRange range = [seachStr rangeOfString:@"234"];//搜索B字符串在A字符串中的范围
 //库中的NSRange(包含了位置和长度的结构体)
//        typedef struct _NSRange {
//        NSUInteger location;
//        NSUInteger length;
//        } NSRange;
        NSLog(@"%d,%d,%lu,%lu",f,f1,(range.location),(range.length));//位置  长度  (unsigned long)
        
        if (range.location == NSNotFound)
        {
            NSLog(@"没找到");
        }

6.字符串的裁剪

        NSString *subResource = @"abcde";
        NSString *subStr = [subResource substringFromIndex:3];//从位置1开始剪切字符串，包含1
        NSLog(@"%@",subStr);
        
        NSString *subStr2 = [subResource substringToIndex:3];//剪切到位置3，不包含3，留下3
        NSLog(@"%@",subStr2);

        NSString *subResource = @"abcde";
        NSRange range1 = NSMakeRange(1, 2);
//        range1.location = 1;//位置
//        range1.length = 2;//长度
//等价
//库中的NSMakeRange
//        NS_INLINE NSRange NSMakeRange(NSUInteger loc, NSUInteger len) {
//            NSRange r;
//            r.location = loc;
//            r.length = len;
//            return r;
//        }
        NSString *subStr3 = [subResource substringWithRange:range1];//剪切给定范围的字符串
        //compare方法：1.升序：前 < 后（-1），2.相等0  3.降序：前 > 后（1）
        NSLog(@"%@",subStr3);

7.字符串的比较

       NSLog(@"%d",(NSComparisonResult result = [@"ABC" compare:@"abc"]));
       NSComparisonResult/*枚举类型*/ result = [@"CBA" compare:@"abc" ] ;

       NSLog(@"%ld",result);// NSOrderedAscending = -1L,存储类型L
/*typedef NS_ENUM(NSInteger, NSComparisonResult) {NSOrderedAscending = -1L, NSOrderedSame, NSOrderedDescending};*/

// NSComparisonResult result = [@“” caseInsensitiveCompare:@“”];
不区分大小写的比较

8.字符串元素插入、剔除、替换

        NSString *string = @"Hello World and Sunshine";
        NSString *string1= [string stringByReplacingOccurrencesOfS tring:@"World" withString:@"iBokanWisdom"];
        NSLog(@"替换之前%@替换之后%@",string,string1);

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[])
{
    @autoreleasepool
    {
        NSString *string = @"Hello World and Sunshine";
        NSString *string1= [string stringByReplacingOccurrencesOfString:@"World" withString:@"iBokanWisdom"];
        NSLog(@"替换之前%@替换之后%@",string,string1);
        
        NSRange range = [string rangeOfString:@"World"];//搜索World字符串在Hello World and Sunshine字符串中的范围
        NSString *string3 = [string stringByReplacingCharactersInRange:range withString:@"iBokanWisdom"];//某范围插入字符串
        NSLog(@"%@",string3);
        NSArray *array = [string componentsSeparatedByString:@" " ];//字符串转换为数组
        //array = @[@"Hello",@"World",@"and",@"Sunshine"];
        NSMutableArray *mutableArray = [array mutableCopy];//数组转换
        [mutableArray replaceObjectAtIndex:1 withObject:@"iBokanWisdom"];//iBokanWisdom替换World
//        [NSMutableArray componentsJoinedByString:@" “];
        NSString *string2 = [mutableArray componentsJoinedByString:@" "];//数组转换为字符串
        NSLog(@"%@",string2);
       
    }
    return 0;
}

// NSString构造方法:

//构造方法，语法跟NSNumber,NSArray差不多
stringWithString:
stringWithFormat:@""

//比较

 isEqualTo..

compare

//获取X之前

sub..ToIndex

//截取X到尾

sub..FromIndex

//查找

rangeOf..

NSMutableString篇(注意:可变字符串与不可变字符串的相同操作方法是不同的)

        NSMutableString *mutableString = [[NSMutableString alloc] initWithCapacity/*容量*/:0];//可变字符串初始化
        //首先分配0个存储空间，当字符串长度超出范围后，再去开辟新的存储空间
        [mutableString setString:@"123456"];
        NSString *sstring;//不可变字符串初始化
        sstring = @"123456";//不可变字符串赋值
        [mutableString appendString:@"789"];//可变字符串的追加方法，不产生新的字符串，直接改变原有的字符串
        NSString *welcome = [sstring stringByAppendingString:@"  欢迎你 "];//不可变字符串的追加方法，要产生新的字符串
        NSLog(@"%@--%@",mutableString,welcome);
        //总结:可变字符串只有初始化并且说明长度后才可以对其操作，否则为空

//插入字符串

insertString

//追加字符串

appendString

//替换字符串

deleteCharactersInRange:withString