oneString 和 NSStringThe fundamental difference between

  • StringIs a structure, and a structure is a value type, soStringIt’s also a value type.
  • When a value type is assigned to a variable, constant, or passed to a function, its value is copied. This means that their instances, along with any value type attributes contained in those instances, are copied when passed through the code.
  • NSStringIt’s a class, and a class is a reference type, soNSStringAlso a reference type.
  • When a reference type is assigned to a variable, constant, or passed to a function, its value is not copied. Therefore, the existing instance itself is referred to rather than a copy of it.

twoString 与 NSStringThe unique API

2.1 StringThe unique API

2.1.1 initializationString

        var str = String()
        str = "123456"
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2.1.2 String 的 isEmptyattribute

  • Determines whether the string is empty
        var str = String();
        str = "123456";
        print(str.isEmpty);
        // false
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        var str = String();
        print(str.isEmpty);
        // true
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        var str = "";
        print(str.isEmpty);
        // true
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2.1.3 String 的 sorted()Methods:

  • String sort and output an array of characters
        var str = "215423";
        print(str.sorted()); / / /"1"."2"."2"."3"."4"."5"]
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2.1.4 String 的 filter()methods

  • Filter unwanted characters
        let str = 34 56 "12";
        let filter = str.filter { (char) -> Bool inchar ! =""
        };
        print(filter); / / 123456Copy the code

2.1.5 String 的 enumerated()Methods:

        let str = "123456";
        for data in str.enumerated() {
            print(data);
        }
        
        /*
        (offset: 0, element: "1")
        (offset: 1, element: "2")
        (offset: 2, element: "3")
        (offset: 3, element: "4")
        (offset: 4, element: "5")
        (offset: 5, element: "6") * /Copy the code

2.2 NSStringThe unique API

2.2.1 Initializing oneNSString

        var nsStr = NSString();
        nsStr = "123456";
        print(nsStr);
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        var nsStr = NSString(stringLiteral: "123456");
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        var nsStr = NSString.init(string: "123456");
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2.2.1 NSString 的 boolValueattribute

  • Returns true for non-zero digits that start with Y, Y, T, T, or false
        var nsStr = NSString(stringLiteral: "123456");
        print(nsStr.boolValue);
        //true
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2.2.2 NSString 的 isEqual()methods

  • Determines whether two strings are equal
        var nsStr = NSString(stringLiteral: "123456");
        print(nsStr.isEqual(to: "123456"));
        //true
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2.2.3 NSStringNumerical properties of

        var nsStr = NSString(stringLiteral: "123456")
        print(nsStr.intValue);
        print(nsStr.floatValue);
        print(nsStr.doubleValue);
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2.3 String 与 NSStringDifferent written APIS that do the same thing

2.3.1 Obtaining the number of characters in a string

        print(str.count); / / 6print( nsStr.length); / / 6Copy the code

2.3.2 Intercepting a string

  • String Substring is returned after intercepting
        var str = "123456";
        print(str.prefix(str.count - 2));   //"1234"
        print(str.suffix(3));   //"456"
        print(str.dropLast(4)); //"12"
        print(str.dropFirst(2));    //"3456"
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  • NSString Interception completed Mandatory String
        var nsStr = NSString(stringLiteral: "123456");
        print(nsStr.substring(to: nsStr.length - 3))    //"123"
        print(nsStr.substring(from: 3)) //"456"
        print(nsStr.substring(with: NSMakeRange(1, 4))) //"2345"
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2.3.3 Adding Characters to the End of a String

  • String is adding characters to itself
        var str = "123456";
        str.append("abc");
        print(str);
        //123456abc
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  • NSString is returning a new String that doesn’t change itself
        var nsStr = NSString(stringLiteral: "123456");
        let nsStr1 = nsStr.appending("abc");
        print(nsStr); / / 123456print(nsStr1);  //123456abc
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2.4 String 与 NSStringThe same API

2.4.1 Whether the prefix/suffix is specified

        var str = "123456";
        str.hasPrefix("12") / /true
        str.hasSuffix("56") / /true
        
        var nsStr = NSString(stringLiteral: "123456");
        nsStr.hasPrefix("12") / /true
        nsStr.hasSuffix("56") / /true
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2.4.2 Splitting strings with specific characters

        var str = "The 123456-11";
        str.components(separatedBy: "-"); / / /"123456"."11"]

        var nsStr = NSString(stringLiteral: "123456-22");
        nsStr.components(separatedBy: "-"); / / /"123456"."22"]
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2.4.3 Case conversion

        var str = "abc";
        print(str.uppercased());    //ABC
        print(str.lowercased());    //abc
        
        var nsStr = NSString(stringLiteral: "cba");
        print(nsStr.uppercased);    //CBA
        print(nsStr.lowercased);    //cba
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2.4.4 Capitalize the first letter

        var str = "abc";
        print(str.capitalized);    //Abc
        
        var nsStr = NSString(stringLiteral: "cba");
        print(nsStr.capitalized);    //Cba
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2.4.5 Removing a specific string

  • The blank space.whitespaces
  • A newline.newlines
  • digital.decimalDigits
  • The letter.letters
  • The capital letters.uppercaseLetters
        let str = "\r abc ";
        let strTrimed = str.trimmingCharacters(in: .whitespacesAndNewlines)
        print(strTrimed);   //abc
        
        let nsStr = NSString(stringLiteral: "\r cba ");
        let nsStrTrimed = nsStr.trimmingCharacters(in: .whitespacesAndNewlines);
        print(nsStrTrimed); //cba
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2.4.6 Character replacement

  • If the character you want to replace cannot be found, the original string is returned
        let str = "hello String";
        let str1 = str.replacingOccurrences(of: "String", with: "world")
        print(str1) //"hello world"
        
        let nsStr = NSString(stringLiteral:"hello NSString");
        let nsStr1 = nsStr.replacingOccurrences(of: "NSString", with: "world")
        print(nsStr1)   //"hello world"
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2.4.7 Ten \ 16 \ octal number turn string

  • Result Mandatory String
        let hexStr = String().appendingFormat("%x",16)// Convert decimal to hexadecimal, the result is"10"
        let oStr = String().appendingFormat("%o",16)// Convert decimal to octal, resulting in"20"
        let dStr = String().appendingFormat("%d",0x10)// Convert hexadecimal to decimal, and the result is"16"
        let dStr1 = String(format: "%d", 0o10)// Convert octal to decimal, resulting in"8"
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  • The result is an NSString
        let hexNSStr = NSString().appendingFormat("%x", 16)// Convert decimal to hexadecimal, the result is"10"
        let oNSStr = NSString().appendingFormat("%o",16)// Convert decimal to octal, resulting in"20"
        let dNSStr = NSString().appendingFormat("%d",0x10)// Convert hexadecimal to decimal, and the result is"16"
        let dNSStr1 = NSString(format: "%d", 0o10)// Convert octal to decimal, resulting in"8"
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