i need to take only the integer from a string like this "Critical: 3\r\n" , note that the value change everytime so i can't search for "3", i need to search for a generic int.
Thanks.
Many ways to do it. There are already some answers. Here is one more approach:
let s = "Critical: 3\r\n";
let s_res = s.split(":").collect::<Vec<&str>>()[1].trim();
println!("s_res = {s_res:?}"); // "3"
In the above code s_res will be a string (&str). To convert that string to an integer, you can do something like this:
let n: isize = s_res.parse().expect("Failed to parse the integer!");
println!("n = {n}"); // 3
Note that, depending on your needs, you might want to add some extra validations/asserts, in case you expect the pattern might change (for example, the number of colons not to be 1, etc.).
Building on #AlexanderKrauze's comment the most common way to do so is using a regex, which lets you look for any pattern in a String:
let your_text = "Critical: 3\r\n";
let re = Regex::new(r"\d+").unwrap(); // matches any amount of consecutive digits
let result:Option<Match> = re.find(your_text);// returns the match
let number:u32 = result.map(|m| m.as_str().parse::<u32>().unwrap()).unwrap_or(0); // converts to int
print!("{}", number);
would be the code for that. Only one digit is r"\d".
More documentation is found here.
You can use chars to get an iterator over the chars of a string, and then apply filter on that iterator to filter out only digits(is_digit).
fn main() {
let my_str: String = "Critical: 3\r\n".to_owned();
let digits: String = my_str.chars().filter(|char| char.is_digit(10)).collect();
println!("{}", digits)
}
Related
Say I have a str s with the value foo004Frtz and I want to use an iterator to parse the string.
Goal is to in the end parse the 004F into a u16.
let it = s.chars().into_iter();
Assuming that it is at the correct position (second o), how do I parse the u16 from the iterator?
I tried:
let x = u16::from_str_radix(hex, 16); // Should be set to 79
but have a hard time constructing hex from the iterator.
EDIT:
Make value a bit more complicated.
Thx to #Chayim I figured out one solution:
let hex = &it.as_str()[..4];
let x = u16::from_str_radix(&hex, 16).unwrap();
Not sure though how efficient as_str() is...
I am trying to write a program that takes a list of words and then, if the word has an even length, prints the two middle letters. If the word has an odd length, it prints the single middle letter.
I can find the index of the middle letter(s), but I do not know how to use that index to print the corresponding letters of the word.
fn middle(wds: &[&str)){
for word in wds{
let index = words.chars().count() /2;
match words.chars().count() % 2{
0 => println!("Even word found"),
_ => println!("odd word found")
}
}
}
fn main(){
let wordlist = ["Some","Words","to","test","testing","elephant","absolute"];
middle(&wordlist);
}
You can use slices for this, specifically &str slices. Note the &.
These links might be helpful:
https://riptutorial.com/rust/example/4146/string-slicing
https://doc.rust-lang.org/book/ch04-03-slices.html
fn main() {
let s = "elephant";
let mid = s.len() / 2;
let sliced = &s[mid - 1..mid + 1];
println!("{}", sliced);
}
Hey after posting i found two different ways of doing it, the fact i had two seperate ways in my head was confusing me and stopping me finding the exact answer.
//i fixed printing the middle letter of the odd numbered string with
word.chars().nth(index).unwrap()
//to fix the even index problem i did
&word[index-1..index+1]
I am doing some processing of a string in Rust, and I need to be able to extract the last set of characters from that string. In other words, given a string like the following:
some|not|necessarily|long|name
I need to be able to get the last part of that string, namely "name" and put it into another String or a &str, in a manner like:
let last = call_some_function("some|not|necessarily|long|name");
so that last becomes equal to "name".
Is there a way to do this? Is there a string function that will allow this to be done easily? If not (after looking at the documentation, I doubt that there is), how would one do this in Rust?
While the answer from #effect is correct, it is not the most idiomatic nor the most performant way to do it. It'll walk the entire string and match all of the |s to reach the last. You can make it better, but there is a method of str that does exactly what you want - rsplit_once():
let (_, name) = s.rsplit_once('|').unwrap();
// Or
// let name = s.rsplit_once('|').unwrap().1;
//
// You can also use a multichar separator:
// let (_, name) = s.rsplit_once("|").unwrap();
// But in the case of a single character, a `char` type is likely to be more performant.
Playground.
You can use the String::split() method, which will return an iterator over the substrings split by that separator, and then use the Iterator::last() method to return the last element in the iterator, like so:
let s = String::from("some|not|necessarily|long|name");
let last = s.split('|').last().unwrap();
assert_eq!(last, "name");
Please also note that string slices (&str) also implement the split method, so you don't need to use std::String.
let s = "some|not|necessarily|long|name";
let last = s.split('|').last().unwrap();
assert_eq!(last, "name");
I have this string:
Some text: $ 12.3 9
I want to get as a result:
12.39
I have found examples on how to keep only numbers, but here I am wanting to keep the decimal point "."
What's a good way to do this in Swift?
This should work (it's a general approach to filtering on a set of characters) :
[EDIT] simplified and adjusted to Swift3
[EDIT] adjusted to Swift4
let text = "$ 123 . 34 .876"
let decimals = Set("0123456789.")
var filtered = String( text.filter{decimals.contains($0)} )
If you need to ignore anything past the second decimal point add this :
filtered = filtered.components(separatedBy:".") // separate on decimal point
.prefix(2) // only keep first two parts
.joined(separator:".") // put parts back together
Easiest and simplest reusable way: you can use this regex replacement option. This replaces all characters except 0 to 9 and dot (.) .
let yourString = "$123. 34"
//pattern says except digits and dot.
let pattern = "[^0-9.]"
do {
let regex = try NSRegularExpression(pattern: pattern, options: NSRegularExpressionOptions.CaseInsensitive)
//replace all not required characters with empty string ""
let string_With_Just_Numbers_You_Need = regex.stringByReplacingMatchesInString(yourString, options: NSMatchingOptions.WithTransparentBounds, range: NSMakeRange(0, yourString.characters.count), withTemplate: "")
//your number converted to Double
let convertedToDouble = Double(string_With_Just_Numbers_You_Need)
} catch {
print("Cant convert")
}
One possible solution to the question follows below. If you're working with text fields and currency, however, I suggest you take a look at the thread Leo Dabus linked to.
extension String {
func filterByString(myFilter: String) -> String {
return String(self.characters.filter {
myFilter.containsString(String($0))
})
}
}
var a = "$ 12.3 9"
let myFilter = "0123456789.$"
print(a.filterByString(myFilter)) // $12.39
I'm starting to like the Swift string formatting since it uses variable names in the string rather than ambiguous formatting tags like "%#"
I want to load a large string from a file that has Swift-style formatting in it (like this)
Now is the time for all good \(who) to come to babble incoherently.
Then I want to feed the contents of that String variable into a statement that lest me replace
\(who)
with the contents of the constant/variable who at runtime.
The code below works with a string constant as the formatting string.
let who = "programmers"
let aString = "Now is the time for all good \(who) to come to babble incoherently."
That code does formatting of a quoted string that appears in-line in my code.
Instead I want something like the code
let formatString = "Now is the time for all good %# to come to babble incoherently."
aString = String(format: formatString, who)
But where I can pass in a Swift-style format string in a constant/variable I read from a file.
Is that possible? I didn't have any luck searching for it since I wasn't exactly sure what search terms to use.
I can always use C-style string formatting and the String class' initWithFormat method if I have to...
I don't think there's a way to do this. String interpolation is implemented via conforming to the StringInterpolationConvertible protocol, and presumably you're hoping to tap into that in the same way you can tap into the methods required by StringLiteralConvertible, a la:
let someString = toString(42)
// this is the method String implements to conform to StringLiteralConvertible
let anotherString = String(stringLiteral: someString)
// anotherString will be "42"
print(anotherString)
Unfortunately, you can't do quite the same trick with StringInterpolationConvertible. Seeing how the protocol works may help:
struct MyString: Printable {
let actualString: String
var description: String { return actualString }
}
extension MyString: StringInterpolationConvertible {
// first, this will get called for each "segment"
init<T>(stringInterpolationSegment expr: T) {
println("Processing segment: " + toString(expr))
actualString = toString(expr)
}
// here is a type-specific override for Int, that coverts
// small numbers into words:
init(stringInterpolationSegment expr: Int) {
if (0..<4).contains(expr) {
println("Embigening \(expr)")
let numbers = ["zeo","one","two","three"]
actualString = numbers[expr]
}
else {
println("Processing segment: " + toString(expr))
actualString = toString(expr)
}
}
// finally, this gets called with an array of all of the
// converted segments
init(stringInterpolation strings: MyString...) {
// strings will be a bunch of MyString objects
actualString = "".join(strings.map { $0.actualString })
}
}
let number = 3
let aString: MyString = "Then shalt thou count to \(number), no more, no less."
println(aString)
// prints "Then shalt thou count to three, no more, no less."
So, while you can call String.init(stringInterpolation:) and String.init(stringInterpolationSegment:) directly yourself if you want (just try String(stringInterpolationSegment: 3.141) and String(stringInterpolation: "blah", "blah")), this doesn't really help you much. What you really need is a facade function that coordinates the calls to them. And unless there's a handy pre-existing function in the standard library that does exactly that which I've missed, I think you're out of luck. I suspect it's built into the compiler.
You could maybe write your own to achieve your goal, but a lot of effort since you'd have to break up the string you want to interpolate manually into bits and handle it yourself, calling the segment init in a loop. Also you'll hit problems with calling the combining function, since you can't splat an array into a variadic function call.
I don't think so. The compiler needs to be able to resolve the interpolated variable at compile time.
I'm not a Swift programmer, specifically, but I think you can workaround it to something pretty close to what you want using a Dictionary and standard string-replacing and splitting methods:
var replacement = [String: String]()
replacement["who"] = "programmers"
Having that, you can try to find the occurrences of "\(", reading what is next and prior to a ")", (this post can help with the split part, this one, with the replacing part), finding it in the dictionary, and reconstructing your string from the pieces you get.
this one works like a charm:
let who = "programmers"
let formatString = "Now is the time for all good %# to come to babble incoherently."
let aString = String(format: formatString, who)