Swift基础语法-字符和字符串--对比OC

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本节知识点

1. 字符
2. 字符串
3. 字符串常用方法
   1. 遍历字符串中的所有字符
   2. 计算字符串长度
   3. 字符串拼接
   4. 格式化字符串
   5. 字符串比较
   6. 判断前后缀
   7. 大小写转换
   8. 转换为基本数据类型
   9. 字符串和数组转换
   10. 字符串包含索引
   11. 字符串替换
   12. 字符串的截取

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1. 字符

• 对比 OC 与 Swift 中字符的区别

char charValue = 'a';//OC当中的字符:

var charValue1:Character = "a" //swift当中的字符:

• Swift和OC字符不一样
  • 1.Swift是用双引号
  • 2.Swift中的字符类型和OC中的也不一样
    • OC中的字符占一个字节,因为它只包含ASCII表中的字符
    • Swift中的字符除了可以存储ASCII表中的字符还可以存储unicode字符.
    • OC的字符是遵守ASCII标准的,
    • Swift的字符是遵守unicode标准, 所以可以存放世界上所有国家语言的字符(大部分)

char charValue = '豪'; //OC当中:错误

var charValue2:Character = "豪" //swift当中: 正确

• 注意: 双引号中只能放一个字符, 如下是错误写法

var charValue3:Character = "ab" // 直接报错

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2. 字符串

• C OC Swift三种语法的对比较

//C: 
char *stringValue = "ab";
char stringArr = "ab";

//OC:
NSString *stringValue = "ab";

//Swift
var stringValue1 = "ab"

• C语言中的字符串是以\0结尾的, 例如:

char *stringValue = "abc\0bcd";
printf("%s", stringValue);
//输出结果: abc

• OC语言中的字符串也是以\0结尾的, 例如:

NSString *stringValue = @"abc\0bcd";
NSLog(@"%@", stringValue);

• swift当中的字符串和C语言/OC语言中的字符串是不一样的, 不是一\0结束

var stringValue = "abc\0bcd"
print(stringValue)
//输入结果: abcbcd

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3. 字符串常用方法

3.1 遍历字符串中的所有字符

let str = "CD豪"
// 遍历字符串中所有的字符
for c in str.characters{
    print(c)
}
// 输出结果:
//C
//D
//豪

3.2 计算字符串长度

• C

//C:
char *stringValue = "CD豪";
printf("%tu", strlen(stringValue));
//输出结果:5

• OC

//OC:
NSString *stringValue = @"CD豪";
NSLog(@"%tu", stringValue.length);
//输出结果:3    以UTF16计算

• Swift

let str = "CD豪"
// 获取字符串的长度
let length = str.characters.count // 计算字符个数
let blen = str.lengthOfBytesUsingEncoding(NSUTF8StringEncoding)// 计算字符串的字节数
print(length) // 3
print(blen)   // 5

3.3 字符串拼接

• C

//C:
char str1[] = "abc";
char *str2 = "bcd";
char *str = strcat(str1, str2);
printf("%s",str);
//输出结果: abcbcd

• OC

//OC:
NSMutableString *str1 = [NSMutableString stringWithString:@"abc"];
NSString *str2 = @"bcd";
[str1 appendString:str2];
NSLog(@"%@", str1);
//输出结果: abcbcd

• Swift

//swift:
var str1 = "chen";
var str2 = "dehao";
var str = str1 + str2;
print(str)
//输出结果:chendehao

3.4 格式化字符串

• OC

//OC:
NSString *str =
[NSMutableString
stringWithFormat:@"http://blog.csdn.net/chendehao001/pic/%tu.png", @10];
NSLog(@"%@", str);
//输入结果: http://blog.csdn.net/chendehao001/pic/10.png

• Swift

//swift:
var index = 10
var str3 = "http://blog.csdn.net/chendehao001/pic/\(index).png"
print(str3)
//输入结果: http://blog.csdn.net/chendehao001/pic/10.png

// 拼接过程格式化
let min = 1
let second = 3
// 注意 format: ,arguments: 这个方法中的 aguments 不要敲错, 没有提示, 如果写错就不会现相应输出, 也不会报错哦
let timeStr = String(format: "%02d:%02d", arguments: [min,second])
print(timeStr) // 输出结果

3.5 字符串比较

• OC

//oc:
NSString *str1 = @"abc";
NSString *str2 = @"abc";
if ([str1 compare:str2] == NSOrderedSame){
    NSLog(@"相等");
}else{
    NSLog(@"不相等");
}
//输出结果:相等

// oc
NSString *str1 = @"abc";
NSString *str2 = @"abc";
if ([str1 isEqualToString:str2]){
    NSLog(@"相等");
}else{
    NSLog(@"不相等");
}
//输出结果:相等

• Swift

//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");
}
//输出结果:相等

var str6 = "abd";
var str7 = "abc";
if str6 >= str7{
    print("大于等于");
}else{
    print("不大于等于");
}
//输出结果: 大于等于

3.6 判断前后缀

• OC

//OC:
NSString *str = @"http://blog.csdn.net/chendehao001";
if ([str hasPrefix:@"http"]) {
    NSLog(@"是url");
}
if ([str hasSuffix:@"chendehao001"]) {
    NSLog(@"是顶级域名");
}
//输出结果: 
//是url
//是顶级域名

• Swift

//Swift:
var str8 = "http://blog.csdn.net/chendehao001"
if str8.hasPrefix("http") {
    print("是url");
}
if str8.hasSuffix("chendehao001") {
print("是顶级域名");
}
//输出结果: 
//是url
//是顶级域名

3.7 大小写转换

• OC

//OC:
NSString *str = @"abc.txt";
NSLog(@"%@", [str uppercaseString]);
NSLog(@"%@", [str lowercaseString]);
//输出结果: ABC.TXT
//abc.txt

• Swift

// 转换大小写
var str8 = "chendehao.TEXT" 
print(str8.uppercaseString) // 输出结果 CHENDEHAO.TEXT
print(str8.lowercaseString) // 输出结果 chendehao.text

• 首字符大写

var str1 = "Chen"
var str2 = "dehao"
print(str1.capitalizedString) // 输出结果 : Chen
print(str2.capitalizedString) // 输出结果 : Dehao

3.8 转换为基本数据类型

• OC

//OC:
NSString *str = @"250";
NSInteger number = [str integerValue];
NSLog(@"%tu", number);
//输出结果: 250

• Swift

// swift
//如果str不能转换为整数, 那么可选类型返回nil
var str10 = "250"
//str10 = "250sb" 不能转换所以可能为nil
var number:Int? = Int(str10)
if number != nil{
    //以前的版本println会自动拆包, 现在的不会
    print(number!)
}

var str9 = "250"
var number1: Int? = Int(str9) // Optional(250)
var number1fromStr = (str9 as NSString).integerValue  // 250
var number2: Int = Int(str9)! //250
var number3  = Int(str9)  //Optional(250)

var str10 = "250sb"
var number4:Int? = Int(str10)  // nil
var number5 = Int(str10) // nil

var str11 = "100"
var sr1 = (str11 as NSString).integerValue //Swift 2.0 //=100
var a = (str11 as NSString).intValue //=100
var l = (str11 as NSString).longLongValue //=100

var str12 = "10.8"
var f = (str12 as NSString).floatValue //=10.8
var d = (str12 as NSString).doubleValue //=10.8

var str13 = "true"
var b = (str13 as NSString).boolValue //=true  // BOOL 类型

3.9 字符串和数组转换

var str1WillTransform = "boy, girl, man, woman"
let strTransformArray = str1WillTransform.componentsSeparatedByString(",")
print(strTransformArray) // ["boy", " girl", " man", " woman"]

var str2WillTransform = "boy,girl,man 10 20 30"
let charset = NSCharacterSet(charactersInString:", ") // 注意: 双引号里有逗号和空格
let str2Array = str2WillTransform.componentsSeparatedByCharactersInSet(charset)
print(str2Array) //["boy", "girl", "man", "10", "20", "30"]

3.10 字符串包含索引

//字符串包含
var str2 = "dehao"
var str5 = "chendehao"
let rangeOfString = str5.rangeOfString(str2)
print(rangeOfString!)// 结果: 4..<9
let startIndex = rangeOfString?.startIndex
print(startIndex!)  // 结果: 4

3.11 字符串替换 replace

• 根据索引位置做替换

var strReplace = "My name is Aarak"
// swift3.0 将移除的的写法
let subRange = Range(start: strReplace.startIndex,end: strReplace.startIndex.advancedBy(2)) 
strReplace.replaceRange(subRange, with: "Your")
print(strReplace) // Your name is Aarak

// 推荐写法
let subRange1 = Range(strReplace.startIndex ..< strReplace.startIndex.advancedBy(4)) 
strReplace.replaceRange( subRange1, with: "CDH")
print(strReplace) // CDH name is Aarak

• 通过字符串收索做替换

// 区分大小写搜索与替换
var str2Replace = strReplace.stringByReplacingOccurrencesOfString("Aarak", withString: "CD豪")
print(str2Replace) // CDH name is Aarak --> CDH name is CD豪

// 不分大小写搜索与替换
str2Replace = strReplace.stringByReplacingOccurrencesOfString("aaraK", withString: "DeHAO陈",options: NSStringCompareOptions.CaseInsensitiveSearch,range: nil)
print(str2Replace) // CDH name is Aarak --> CDH name is DeHAO陈

3.12 字符串的截取

• 转化为 OC 的语法做字符串截取

// 截取字符, 方式一:
let urlString = "http://blog.csdn.net/chendehao001"
let header = (urlString as NSString).substringToIndex(4) // http
let footer = (urlString as NSString).substringFromIndex(21) // chendehao001
let range = NSMakeRange(21, 9) //
let middle = (urlString as NSString).substringWithRange(range) // chendehao
print(middle) //chendehao

• 直接使用 Swift 提供的语法做截取

// 截取字符, 方式二:
let endIndex = urlString.startIndex.advancedBy(21)
let starIndex = urlString.endIndex.advancedBy(-3)
let header1 = urlString.substringToIndex(endIndex)
let footer1 = urlString.substringFromIndex(starIndex)

// Range(start: ,end: ) 这个写法在 Swift3.0 移除
let range1 = Range(start: endIndex.advancedBy(0),end: starIndex.advancedBy(-0))
let middle1 = urlString.substringWithRange(range1)
print(middle1) // chendehao

• 推荐写法

let range2 = Range( urlString.startIndex.advancedBy(21) ..< urlString.endIndex.advancedBy(-3))
let middle2 = urlString.substringWithRange(range2)
print(middle2) // chendehao

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