字符串常用方法

/*

 计算字符串长度:

 C:

 char *stringValue = "abc李";

 printf("%tu", strlen(stringValue));

 打印结果6

 

 OC:

 NSString *stringValue = @"abc李";

 NSLog(@"%tu", stringValue.length);

 打印结果4, 以UTF16计算

*/

var stringVlaue = "abc韩"

print(stringVlaue.lengthOfBytes(using: String.Encoding.utf8))

// 打印结果:6, 和C语言一样计算字节数

 

/*

 字符串拼接

 C:

 char str1[] = "abc";

 char *str2 = "bcd";

 char *str = strcat(str1, str2);

 

 OC:

 NSMutableString *str1 = [NSMutableString stringWithString:@"abc"];

 NSString *str2 = @"bcd";

 [str1 appendString:str2];

 NSLog(@"%@", str1);

 

*/

var str1 = "abc"

var str2 = "hjq"

var str = str1 + str2

print(str)

 

/*

 格式化字符串

 C: 相当麻烦, 指针, 下标等方式

 OC:

 NSInteger index = 1;

 NSString *str1 = [NSMutableString stringWithFormat:@"http://ios.520it.cn/pic/%tu.png", index];

 NSLog(@"%@", str1);

*/

var index = 1

var str3 = "http://www.blog26.com/pic/\(index).png"

print(str3)

 

/*

 字符串比较:

 OC:

 NSString *str1 = @"abc";

 NSString *str2 = @"abc";

 if ([str1 compare:str2] == NSOrderedSame)

 {

 NSLog(@"相等");

 }else

 {

 NSLog(@"不相等");

 }

 

 if ([str1 isEqualToString:str2])

 {

 NSLog(@"相等");

 }else

 {

 NSLog(@"不相等");

 }

 

 Swift:(== / != / >= / <=), 和C语言的strcmp一样是逐个比较

*/

 

var str4 = "abc"

var str5 = "abc"

if str4 == str5

{

    print("相等")

}else

{

    print("不相等")

}

 

var str6 = "abd"

var str7 = "abc"

if str6 >= str7

{

    print("大于等于")

}else

{

    print("不大于等于")

}

 

/*

 判断前后缀

 OC:

 NSString *str = @"http://www.blog26.com";

 if ([str hasPrefix:@"http"]) {

 NSLog(@"是url");

 }

 

 if ([str hasSuffix:@".com"]) {

 NSLog(@"是天朝顶级域名");

 }

*/

var str8 = "http://www.blog26.com"

if str8.hasPrefix("www")

{

    print("是url")

}

if str8.hasSuffix(".com")

{

    print("是顶级域名")

}

 

/*

 大小写转换

 OC:

 NSString *str = @"abc.txt";

 NSLog(@"%@", [str uppercaseString]);

 NSLog(@"%@", [str lowercaseString]);

*/

var str9 = "abc.txt"

print(str9.uppercased())

print(str9.lowercased())

 

/*

 转换为基本数据类型

 OC:

 NSString *str = @"250";

 NSInteger number = [str integerValue];

 NSLog(@"%tu", number);

*/

var str10 = "250"

// 如果str不能转换为整数, 那么可选类型返回nil

// str = "250sd", 不能转换所以可能为nil

var numerber:Int? = Int(str10)

if numerber != nil

{

    print(numerber!) // 2.0可以自动拆包,3.0以后则不会

}