Swift String Common Method _swift Foundation

Refer to the Java String class for a summary of swift string usage.

Basic article:

1, String length: 3 ways.

let-str = "12345678" let
len1 = strlen (str)//8 let
len2 = Str.count  //8 let
len3 = (str as nsstring). Leng Th  //8

2, string concatenation: Use the plus or append function.

Let str1 = "abc" + "CDE"
var str = "abc"
Str.append ("CDE")

3. String Traversal:

Let str = ' ABCDEFG ' for
char in str {
    print (char)
}

Let str = ' ABCDEFG ' for
index in str.indices.indices {
    print (Str[index])   ///through subscript access
}

or subscript

Let str = ' ABCDEFG '
for (index, value) in str.enumerated () {
    print ("\ Index---\ (value)")
}

4, all uppercase or lowercase strings:

Let str = "ABCDEFG"
print (str.lowercased ())  //All lowercase
print (str.uppercased ())  //ALL CAPS

5, multiline string uses 3 double quotes.

let-verse = "" "
    to be, or not to be-that is the question;
    Whether ' tis nobler
    in the mind to suffer the slings and arrows of outrageous fortune,
    or to take arms against Sea of Troubles, "" "" ""

6. ASCII code

Let ASCII = Unicodescalar ("a")?   ASCII code
print (ASCII??) for value//a. "")//97

7. Intercept substring

Let str = ' ABCDEFG ' let
indexd = Str.index (of: ' d ') let
sub = str[indexd!...]//DEFG let
sub1 = Str[indexd!.. <str.endindex]//DEFG  pay attention to avoid subscript out of bounds let
sub2 = str[str.startindex...indexd!]//abcd

Or

Let sub3 = (str as nsstring). substring (to:3)  //abc let
sub4 = (str as nsstring). Substring (With:nsmakerange (2, 3) )  //CDE

8, judge whether contains the character (string)

Let str = "ABCDEFG"
print (Str.contains ("CD"))   //true
print (Str.contains ("C"))    //true
Print (Str.contains ("O"))    //false

9, String segmentation

String splitting (delimited by single or multiple characters) let
str = "abcdefg$ $aaaa $ $BBBB $ $CCC" let
des1 = (str as nsstring). Components (Separatedby : "$$") let
des2 = str.components (separatedby: "$$")
print (des1)  //["ABCDEFG", "AAAA", "bbbb", "CCC"]
Print (Des2)//["ABCDEFG", "AAAA", "bbbb", "CCC"]

10. String Replacement:

Let str = "abcdefg$ $aaaa $ $BBBB $ $ccc ' let
dest11 = str.replacingoccurrences (of: ' $$ ', with:" * * ")
print (dest11)

Advanced Chapter:
1. Get subscript characters:

Extension String {
    //get subscript corresponding character
    func charAt (pos:int)-> Character? {
        If pos < 0 | | | pos >= count {return
            nil   //Judge boundary condition
        } let
        index = Self.index (self.startindex , offsetby:pos) let
        str = self[index] return
        Character (String (str)}} let
str = "ABCdef" C20/>print (Str.charat (pos:1)!)  B

2. Find the longest substring in the string, including Chinese, special characters, letters, numbers, and so on. Idea: use regular to find all the strings, and then sort by length to find the longest.

Find the longest-
func Longestword (_ sen:string)-> string {let
    regx = try? Nsregularexpression (pattern: [a-za-z]+], options:. caseinsensitive)
    
    if let results = regx? Matches (In:sen, Options: [], Range:nsmakerange (0, Sen.count)) {
        var array: [String] = [] for
        item in results {
  let cur = (sen as NSString). substring (with:item.range)
            array.append (cur)  //Find all strings
        that meet the requirements Array.Sort (by: {a,b in
            if A.count > B.count {     //descending order return
                true
            } else {return
                false
            return
        
        array[0]  //Longest string
    } return
    
    sen} let

ret = Longestword (' This is a test demo.1234324234 interspersed with Chinese and special letters @#@ #adfsdfsdf!@#@ $adfsdf ")
print (ret)  //ADFSDFSDF

3. Capitalize the first letter of the string (consider punctuation in the string):

Initials, requiring support for punctuation
func lettercapitalize (_ str:string)-> String {
    
    var result = "" For

    I in 0..<str.count{ Let
        cur = Str.charat (pos:i)

        if i = = 0 {let
            tmp = String (cur!). uppercased ()  //To uppercase
            Result.append (TMP)
        } else {let
            pre = Str.charat (pos:i-1)
            //if pre was not Character
            if (Unicodescalar String (pre!))!. Value >= unicodescalar ("a")!. Value && unicodescalar (String (pre!))!. Value <= unicodescalar ("Z")!. Value)
                | | (Unicodescalar (String (pre!))!. Value >= unicodescalar ("A")!. Value && unicodescalar (String (pre!))!. Value <= unicodescalar ("Z")!. Value) {
                result.append (string (cur!))
            } else {
                result.append (cur!). Uppercased ())}} return result
            
        } let
ret = lettercapitalize (' This a test message ')
Print (ret)

4, get the Uilable control to display the height required by the string

Extension String {
    /**
     * Query lable height
     * @param fontsize, font size
     * @param width, lable width
    * * * func Getlableheightbywidth (_ Fontsize:cgfloat,
                               width:cgfloat,
                               font:uifont)-> cgfloat {let
        size = Cgsize ( Width:width, Height:CGFloat.greatestFiniteMagnitude) let
        paragraphstyle = Nsmutableparagraphstyle ()
        Paragraphstyle.linebreakmode =. bywordwrapping let
        attributes = [Nsfontattributename:font,
                          NSParagraphStyleAttributeName:paragraphStyle.copy ()] let
        
        text = self as nsstring let
        rect = Text.boundingrect (With:size, Options:.useslinefragmentorigin, Attributes:attributes, Context:nil) return
        Rect.size.height
    }
    
}