Swift Learning Notes (18)--string string.index and range __swift

In the search for swift strings, it is sometimes possible to return a range rather than a specific location. This will use the concept of range in Swift. We'll take a detailed explanation of this.

(1) Retrieving a Word method in a string: rangeofstring

var str = "Hello Apple.hello Swift"

str.rangeofstring ("Hello")//forward retrieval;

str.rangeofstring ("Hello", Options: Nsstringcompareoptions.backwardssearch)//reverse retrieval;

str.rangeofstring ("swift")/Case exact match

str.rangeofstring (" Swift ", options:NSStringCompareOptions.CaseInsensitiveSearch)//Ignore case

Output results:

。

Results Analysis:

You can see that the rangeofstring return value is a range range. If empty, returns nil. Rangeofstring () method has a lot of parameters to choose from, we can try.

(2) Find a specific string from the specified range of strings

Sometimes, according to our requirements, it is not necessary to retrieve a string from the entire length of the string, possibly in a range, where String.index is used.

var str = "Hello apple.hello Swift" let

startIndex:String.Index = Str.startindex let

endIndex:String.Index = Adva NCE (startIndex) let

strrange = range<string.index> (start:startindex,end:endindex)

Str.rangeofstring ("App", Options:NSStringCompareOptions.CaseInsensitiveSearch, Range:strrange)

Output results:

。

(3) Intercept substring

Swift supports intercepting a string that intercepts a specified length from a location.

var str = "Hello apple.hello Swift"

var toindex = advance (Str.startindex, 4)

Str.substringtoindex (toindex)// Intercepts a string from the beginning to the 4th position;

var fromindex = advance (Str.startindex, 7)

Str.substringfromindex (fromindex)// To intercept from the 7th position to the final string;

Str.substringwithrange (Range<string.index> (Start:toindex, End:fromindex))// Intercepts a string from the 4th position to the 7th position;

Output results:

。

Result analysis: After interception, the original string is unchanged.

(4) Insert character: Insert ()

Swift can insert a character at the specified position of the string. The code is as follows:

var str = "Hello apple.hello Swift"

var insertindex = advance (Str.startindex, 5)//insert Str.insert at 5th position

("!", ATINDEX:INSERTINDEX)//insert an exclamation point

Output results:

。

(5) Remove character: Remove ()

Swift can delete a character at a location specified in the string. The code is as follows:

var str = "Hello apple.hello Swift"

var insertindex = advance (Str.startindex, 5)//insert Str.insert at 5th position

("!", ATINDEX:INSERTINDEX)//Insert an exclamation point

str.removeatindex (insertindex)

str

Output results:

。

Result Analysis: Experiments show that the Insert () method and the Removeatindex () method modify the original string.

(6) Replacement string

In Swift, you can use one string to replace another string, as in the following code:

var str = "Hello Apple.hello Swift"//replace Hello with hi

var replaceendindex = advance (Str.startindex, 5)// From the start character to the fifth character (5 is the open interval)

str.stringbyreplacingcharactersinrange (range<string.index>) (Start:str.startIndex, End:replaceendindex), withstring: "HI")//Replace with HI

Output results:

。

GitHub home: https://github.com/chenyufeng1991. You are welcome to visit.