第一：基本数据类型与字符串转换

//基本数据类型(int float,double char)

1）基本数据类型—>NSString

//1.int类型换换成字符串

int a = 88;

NSString * str1 = [NSString stringWithFormat:@"%d",a];

//2.float -> NSString

float f = 0.8;

NSString * str3 = [NSString stringWithFormat:@"%.1f",f];

//3.double - >NSstring

 double d = 66.2222;

 NSString * str4 = [NSString stringWithFormat:@"%.4f",d];

//4.char - > NSString

char c = ‘b';

NSString * str5 = [NSString stringWithFormat:@"%c",c];

2）NSString-—>基本数据类型     

//5.NSString -> int

 NSString * str6 = @"1";

int i1 = [str6 intValue];

//5.NSString -> float

NSString * str7 = @“8.8";

float f1 = [str7 floatValue];

//6.NSString -> double

NSString * str8 = @"8.88";

double d1 = [str8 doubleValue];

//注意:当你要把字符串转换成某种基本数据类型的时候,一定要确定你要转化你的数据是正确

NSString * str9 = @“a123";

int i2 = [str9 intValue];

//7.将字符串中的字母转换成大写

 NSString * str10 = @“apple";

NSString * tmpStr1 = [str10 uppercaseString];

NSLog(@"tmpStr1 %@ str10 %@",tmpStr1,str10);

//8.将字符中的字母转换成小写

NSString * str11 = @“APPLE";

NSString * tmpStr2 = [str11 lowercaseString];

//9.将首字母大写

NSString * str12 = @“apple";

NSString * tmpStr3 = [str12 capitalizedString];

第二：字符串重组

//1.多个数据拼接成一个字符串

int year = 1990;

int month = 8;

int day = 08;

NSString * date = [NSString stringWithFormat:@"%d年%d月%d日",year,month,day];

NSString * address = @“上海";

NSString * dateAndAddrss = [NSString stringWithFormat:@"%@地址:%@",date,address];

//2.字符串的末尾追加新的字符

NSString * str1 = @"apple.";

NSString * str2 = [str1 stringByAppendingString:@"iphone"];

//3.在指定的范围追加字符串

NSString * str3 = @"apple";

NSRange range = {4,0};

//location代表的时从哪个索引开始插入,length 代表的意思可以覆盖几个字符

NSString * str4 = [str3 stringByReplacingCharactersInRange:range withString:@"iphone"];

//4.使用新的字符,替换原有的字符

NSString * str5 = @“apple,iPhone";

NSString * str6 = [str5 stringByReplacingOccurrencesOfString:@“p" withString:@“q"];

//5.在字符串中删除特定的某些字符 胡汉三 hhs

NSString * str7 = @“apple-iphone—.iwatch.itouch";

NSString * str8 = [str7 stringByReplacingOccurrencesOfString:@"-" withString:@""];

//6.去掉字符串中的空格

NSString * str9 = @“apple iPhone iwatch";

NSString * str10 = [str9 stringByReplacingOccurrencesOfString:@" " withString:@""];

第三： 字符串写入文件

  3.1:将字符串写入到文件

NSString * content = @"今天马路上捡到一分钱";

NSString * path = @"/Users/tengfei/Desktop/test.txt";

//1.NSString *:要给入文件目录(并且要包括文件名称)

//2.atomically : YES

//3.NSUTF8StringEncoding 国际通用的编码格式

//4.NSError 是用来记录错误信息的

NSError * error;

//writeToFile:<#(NSString *)#> atomically:<#(BOOL)#> encoding:<#(NSStringEncoding)#> error:<#(NSError *__autoreleasing *)#>

BOOL result = [content writeToFile:path atomically:YES encoding:NSUTF8StringEncoding error:&error];

if(result)

{

    NSLog(@"文件创建成功");

}

else

{

    NSLog(@"error %@",error);

}

  3.2：从文件中读取字符串内容

  //要给出文件路径

  //你写入文件的时候,使用的是什么编码格式,读取的时候就要用什么编码格式

NSString * path = @"/Users/tengfei/Desktop/test.txt";

NSError * error;

NSString * str = [NSString stringWithContentsOfFile:path encoding:NSUTF8StringEncoding error:&error];

if (error != nil)

{

    NSLog(@"error message %@",error);

}

else

{

    NSLog(@"str content %@",str);

}

第四：可变字符串

//1.创建可变字符串

//NSMutableString 继承自 NSString

//NSMutableString 拥有NSString所有的属性以及方法

//NSMutableString * muStr = [[NSMutableString alloc] init];

NSMutableString * muStr = [[NSMutableString alloc] initWithCapacity:0];

//是初始化字符串内容

[muStr setString:@"apple"];

//动态的给字符串末尾追加新值

[muStr appendString:@".com"];

//在指定的索引位置,插入字符串

[muStr insertString:@“iphone" atIndex:3];

//删除指定范围的字符串

//你要删除的长度,一定不能够超出字符串的的长度,导致异常Range or index out of bounds

NSRange range = {3,7};

// [muStr deleteCharactersInRange:range];

[muStr replaceCharactersInRange:range withString:@"苹果"];