Swift--字符串

一 定义字符串

  oc语言：  NSString *stringValue = "ab";

  swift语言：var stringValue1 = "ab"

       注： oc语言的字符只包含ascii码，每一个字符只占1个字节，字符串是以\0结尾

                swift语言包含unicode字符集，  

二 字符串的使用

计算字符串长度:

OC:

NSString *stringValue = @"abc李";

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

swift：

var stringValue = "abc李"

print(stringValue.lengthOfBytesUsingEncoding(NSUTF8StringEncoding))

  

字符串拼接

OC:

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

NSString *str2 = @"bcd";

[str1 appendString:str2];

NSLog(@"%@", str1);

swift：

var str1 = "abc";

var str2 = "lnj";

var str = str1 + str2;

print(str)

插入字符串

OC:

NSInteger index = 1;

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

NSLog(@"%@", str1);

swift:

var index = 1

var str3 = "http://www.520it.com/pic/\(index).png"

print(str3)

字符串比较:

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:

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");

}

判断先后缀

OC:

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

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

    NSLog(@"是url");

}

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

    NSLog(@"是个什么鸟");

}

swift:

var str8 = "http://www.520it.com"

if str8.hasPrefix("http") {

    print("是url");

}

if str8.hasSuffix(".com") {

    print("是商用网站");

}

大小写转换

OC:

NSString *str = @"abc.txt";

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

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

swift:

var str9 = "abc.txt";

print(str9.uppercaseString)

print(str9.lowercaseString)

转换为基本数据类型

OC:

NSString *str = @"250";

NSInteger number = [str integerValue];

NSLog(@"%tu", number);

swift:

var str10 = "250"

var number:Int? = Int(str10)//若是没有整数，就反悔nil

if number != nil

{

    print(number!)

}