Initializing an empty string
Create an empty string, you can assign an empty string literal to a variable, or you can initialize a new string instance: var emptystring = ""
var anotheremptystring = String ()
Two strings are empty, and equality can be determined by checking the IsEmpty property of its Boolean type whether the string is empty: if Emptystring.isempty {
println ("Nothing")
}
string VariabilityAssign a specific string to a variable to modify it, or assign it to a constant to ensure it is not modified: var variablestring = "Horse"
Variablestring + = "and carriage"
Let constantstring = "Highlander"
Constantstring + = "and another Highlander"//Compile Error Note: In Swift, whether a string can be modified is determined only by defining a variable or constant, which enables the unification of multiple types of variability operations.
string is a value typeThe string type is a value type, a string that is copied when it is passed in a constant, variable assignment operation, or in a function or method. In any case, a new copy of the existing string is created and the new copy is passed or assigned.
using charactersThe string type represents a collection of Character type values for a particular sequence, and you can use for in to iterate through each character in the string. For character in "dog!" {
println (character)
In addition, you can create a separate character constant or variable by indicating a Character type and copying it by character literal: let Yensign:character = "￥"
calculating the number of charactersBy using the global countelements function of the bar, you can get the number of characters in a string let Unusualmenagerie = "Koala, Snail, Penguin, dromedary"
println ("Unusualmenagerie has \ (countelements (Unusualmenagerie)) characters)"
Connection StringYou can connect two strings by "+" let string1 = "Hello"
Let string2 = "there"
var welcome = string1 + string2 You can use "+ =" to append a string to a string variable var instruction = "Look over"
Instruction + = string2//"Look over There" can append a Character variable to a string variable by using the string's Append method Exclamationmark:cha Racter = "!"
Welcome.append (Exclamationmark)//"Hello there!" NOTE: You cannot append a String or Character after a Character variable, because Character can contain only one character
string InterpolationString interpolation is a way to construct a new string that can contain constants, variables, literals, and expressions. Each entry of the inserted string literal is wrapped in "\ ()" In Let multiplier = 3
Let message = "\ (multiplier) times 2.5 is \ (Double (multiplier) * 2.5)" Note: An expression written in parentheses in an interpolated string cannot contain a non-escaped double quotation mark (") and a backslash (\). and cannot contain carriage returns or line feeds.
Comparing StringsThree ways to compare strings: strings are equal, prefixes are equal, suffixes are equal
string EqualityIf two strings contain exactly the same characters in the same order, the two strings are considered equal let quotation = "We ' re a lot alike, you and I"
Let samequotation = "We ' re a lot alike, you and I"
If quotation = = Samequotation {
println ("These, strings is considered equal")
}
The prefix is equalCheck whether a string has a specific prefix or suffix by calling the Hasprefix/hassuffix method of string. Let Remeoandjuliet = [
"Act 1 Scene 1:verona, A public Place",
"Act 1 Scene 2:capulet ' s Mansion",
ACT 1 Scene 3: A Capulet ' s Mansion ",
"Act 1 Scene 4:a Street outside Capulet ' s mansion",
"Act 1 Scene 5:the great Hall in Capulet ' s mansion",
"Act 2 Scene 1:outside Capulet ' s Mansion",
"Act 2 Scene 2:capulet ' s Orchard",
"Act 2 Scene 3:outside friar Lawrence ' s Cell",
"Act 2 Scene 4:a Street in Verona",
"Act 2 Scene 5:capulet ' s Mansion",
"Act 2 Scene 6:friar Lawrence ' s Cell"
]
var act1scenecount = 0
For scene in Remeoandjuliet {
If Scene.hasprefix ("Act 1") {
++act1scenecount;
}
}
println ("There is \ (Act1scenecount) scenes in Act 1")
var mansioncount = 0
var cellcount = 0
For scene in Remeoandjuliet {
If Scene.hassuffix ("Capulet ' s Mansion") {
++mansioncount
} else if Scene.hassuffix ("Friar Lawrence ' s cell") {
++cellcount
}
}
println ("\ (mansioncount) mansion scenes; \ (cellcount) cell scenes ") uppercase and lowercase strings can be accessed through the string's uppercasestring and LowerCaseString properties to access the uppercase \ Lowercase version of the string let normal =" Could you h ELP me, please? "
Let shouty = normal.uppercasestring
Let whispered = normal.lowercasestring
Swift Study notes-3. Strings and characters
