I searched for an answer the entire day but nothing really came close to answering my issue. I am trying to use stringWithFormat in Swift but while using printf format strings. The actual issue I have is with the %s. I can't seem to get to the original string no matter how I try this.
Any help would be much much appreciated (or workarounds).
Things I already did: tried all available encodings for the cString, tried creating an ObjC function to use for this, but when I passed the arguments from Swift I ran into the same strange issue with the %s, even if when hardcoded in the ObjC function body it appears to print the actual correct String.
Please find bellow the sample code.
Many thanks!
var str = "Age %2$i, Name: %1$s"
let name = "Michael".cString(using: .utf8)!
let a = String.init(format: str, name, 1234)
Expected result is quite clear I presume, however I get something like this instead of the correct name:
"Age 1234, Name: ÿQ5"
Use withCString() to invoke a function with the C string
representation of a Swift string. Also note that %ld is the correct
format for a Swift Int (which can be a 32-bit or 64-bit integer).
let str = "Age %2$ld, Name: %1$s"
let name = "Michael"
let a = name.withCString { String(format: str, $0, 1234) }
print(a) // Age 1234, Name: Michael
Another possible option would be to create a (temporary) copy
of the C string representation
(using the fact a Swift string is automatically converted to a C string when passed to a C function taking a const char * parameter,
as explained in String value to UnsafePointer<UInt8> function parameter behavior):
let str = "Age %2$ld, Name: %1$s"
let name = "Michael"
let nameCString = strdup(name)!
let a = String(format: str, nameCString, 1234)
print(a)
free(nameCString)
I assume that your code does not work as expected because name
(which has type [CChar] in your code) is bridged to an NSArray,
and then the address of that array is passed to the string
formatting method.
Use "%1$#" instead of "%1$s", and don't use the cString call.
This works for me:
var str = "Age %2$i, Name: %1$#"
let name = "Michael"
let a = String.init(format: str, name, 1234)
Related
I have a function that takes second from my controller and introInterval from network service. But my codes does not split string that coming from API. But if i put dummy data, it works. I dont know why. Where is the problem ? Both of them works with same string. My aim is to catch up same data with test variable. You can see outputs of them in print lines.
func getCurrentPlayerTimeAndIntroDuration(second: String, introInterval: String?) {
if let introInterval = introInterval {
print(introInterval) //output: "01:38 - 5:00"
let test = "01:38 - 5:00".trimmingCharacters(in: .whitespacesAndNewlines).components(separatedBy: "-")
let introIntervalArray = introInterval.trimmingCharacters(in: .whitespacesAndNewlines).components(separatedBy: "-")
print("test \(test)") //output: ["01:38", "5:00"] correct
print("introIntervalArray \(introIntervalArray)") //output introIntervalArray ["01:38–02:13"] wrong
}
}
I believe you're using the wrong character to separate the string. If you compare the - (Non-ASCII) character from your example //output introIntervalArray ["01:38–02:13"] wrong you will see the – is different than the one you are using to split the string - (ASCII).
This code:
let test = "01:38–02:13".trimmingCharacters(in: .whitespacesAndNewlines).components(separatedBy: "–")
Outputs:
["01:38", "02:13"]
I'll show the code and the output, since it's easier to explain the issue.
Code and output in the commented lines:
let greekLetter = "β"
let string1 = greekLetter
/// string2 is the same as string1 but converted to NSString then back to String
let string2 = String(NSString(string: greekLetter))
print(string1.range(of: greekLetter)!)
/// prints: Index(_rawBits: 0)..<Index(_rawBits: 131072)
print(string2.range(of: greekLetter)!)
/// prints: Index(_rawBits: 0)..<Index(_rawBits: 65536)
The problem: A String that contains a greek letter returns a range that is different from the same String with the same greek letter that was converted to NSString and then back to String again.
Any ideas why?
Why this question is raised:
I'm doing some parsing and I need to find the range of specific string and then insert something else instead of it. Because of wrong ranges returned inserting strings in a wrong position due to wrong lower/upper bound location.
UPDATE 2:
Let's say I have a task: in a given string "β-1" change "1" to "2". And this string comes from the server.
Please look at this code sample:
let wordWithGreekLetter = "β-1"
var string1 = wordWithGreekLetter
let data = """
{ "name" : "\(wordWithGreekLetter)" }
""".data(using: String.Encoding.utf8)
struct User: Decodable {
let name: String
}
let user = try! JSONDecoder().decode(User.self, from: data!)
/// string2 is the same as string1 but decoded from the data
var string2 = user.name
let rangeOfNumberOne1 = string1.range(of: "1")!
string1.removeSubrange(rangeOfNumberOne1)
string1.insert("2", at: rangeOfNumberOne1.lowerBound)
/// RESULT: string1 = "β-2"
let rangeOfNumberOne2 = string2.range(of: "1")!
string2.removeSubrange(rangeOfNumberOne2)
string2.insert("2", at: rangeOfNumberOne2.lowerBound)
/// RESULT: string2 = "β2-"
As Rob explained in Why is startIndex not equal to endIndex shifted to startIndex position in String in Swift?, the raw bits of the index are an implementation detail, and you should not care about that value.
The actual problem is that (quote from Collection):
Saved indices may become invalid as a result of mutating operations.
so that rangeOfNumberOne1/2 may be no longer valid after you call removeSubrange() on the string.
In this particular case this may happen for string2 (which is bridged from an NSString) because removing a character may reorganize the internal storage. But this is pure speculation: what matters only is that the current code exhibits undefined behavior.
If you replace
let rangeOfNumberOne1 = string1.range(of: "1")!
string1.removeSubrange(rangeOfNumberOne1)
string1.insert("2", at: rangeOfNumberOne1.lowerBound)
by
let rangeOfNumberOne1 = string1.range(of: "1")!
string1.replaceSubrange(rangeOfNumberOne1, with: "2")
(and similarly for string2) then you'll get the same result "β-2" for both strings.
I got homework and I can't handle it. What I need?
I have a project that uses two languages (English, Spanish). The project has 2 Locolizable.strings files for two languages.
Example string:
"OrderDetails_IPText" = "IP: %#";
I understand %# is a string or some object, it does not matter. The problem is in people who help me with the translation of texts into different languages.
When they fill in the translation file, they see:
%#
They do not understand what I want to add there. This could be an email address or something else. People who translate the text gave me the task to implement a function that will take into account such nuances. They even offered some implementation, something like this:
func pffffff(format: something, ["key" : value] -> Id : value
Probably it should be an extension for String.
If you do not understand, thanks for watching this question. I did not understand anything.
We advised that you need to change this func:
func L (_ key: String, value: String = "") -> String
{
let str = NSLocalizedString(key, value: value, comment: "")
return str
}
You can create something like this.
extension String {
func yourFunction () {}
}
But I would recommend you not to use %# or any other character in localization string. You can always use replace string function with when the string contains any variable
For eg:
"We have sent an OTP at [VARIABLEA]"
Then while displaying just look for [VARIABLEA] and replace with actual value
I found a way out of this situation.
public extension String {
/* Creates the string representation of the poo with requested size.
- parameter format: string format with key
- returns: localizable string
*/
public init(format: String, keyArguments: [String: Any]) {
self = format
keyArguments.forEach {
self = self.replacingOccurrences(of: "{\($0.key)}", with: "\($0.value)", options: .caseInsensitive)
}
}
}
Was:
let asd = String(format: "Hi, %#! %d", "Arnold", 2)
Now:
let str = String(format: "Hi, {User_Name}! How are you, {user_name}?", keyArguments: ["user_name" : "Arnold", "number": 5.6])
I can't figure out how to load a string from a file and have variables referenced in that string be interpolated.
Let's say a text file at filePath that has these contents:
Hello there, \(name)!
I can load this file into a string with:
let string = String.stringWithContentsOfFile(filePath, encoding: NSUTF8StringEncoding, error: nil)!
In my class, I have loaded a name in: let name = "George"
I'd like this new string to interpolate the \(name) using my constant, so that its value is Hello there, George!. (In reality the text file is a much larger template with lots of strings that need to be swapped in.)
I see String has a convertFromStringInterpolation method but I can't figure out if that's the right way to do this. Does anyone have any ideas?
This cannot be done as you intend, because it goes against type safety at compile time (the compiler cannot check type safety on the variables that you are trying to refer to on the string file).
As a workaround, you can manually define a replacement table, as follows:
// Extend String to conform to the Printable protocol
extension String: Printable
{
public var description: String { return self }
}
var string = "Hello there, [firstName] [lastName]. You are [height]cm tall and [age] years old!"
let firstName = "John"
let lastName = "Appleseed"
let age = 33
let height = 1.74
let tokenTable: [String: Printable] = [
"[firstName]": firstName,
"[lastName]": lastName,
"[age]": age,
"[height]": height]
for (token, value) in tokenTable
{
string = string.stringByReplacingOccurrencesOfString(token, withString: value.description)
}
println(string)
// Prints: "Hello there, John Appleseed. You are 1.74cm tall and 33 years old!"
You can store entities of any type as the values of tokenTable, as long as they conform to the Printable protocol.
To automate things further, you could define the tokenTable constant in a separate Swift file, and auto-generate that file by using a separate script to extract the tokens from your string-containing file.
Note that this approach will probably be quite inefficient with very large string files (but not much more inefficient than reading the whole string into memory on the first place). If that is a problem, consider processing the string file in a buffered way.
There is no built in mechanism for doing this, you will have to create your own.
Here is an example of a VERY rudimentary version:
var values = [
"name": "George"
]
var textFromFile = "Hello there, <name>!"
var parts = split(textFromFile, {$0 == "<" || $0 == ">"}, maxSplit: 10, allowEmptySlices: true)
var output = ""
for index in 0 ..< parts.count {
if index % 2 == 0 {
// If it is even, it is not a variable
output += parts[index]
}
else {
// If it is odd, it is a variable so look it up
if let value = values[parts[index]] {
output += value
}
else {
output += "NOT_FOUND"
}
}
}
println(output) // "Hello there, George!"
Depending on your use case, you will probably have to make this much more robust.
That might be the dumbest Rustlang question ever but I promise I tried my best to find the answer in the documentation or any other place on the web.
I can convert a string to a vector of bytes like this:
let bar = bytes!("some string");
Unfortunately I can't do it this way
let foo = "some string";
let bar = bytes!(foo);
Because bytes! expects a string literal.
But then, how do I get my foo converted into a vector of bytes?
(&str).as_bytes gives you a view of a string as a &[u8] byte slice (that can be called on String since that derefs to str, and there's also String.into_bytes will consume a String to give you a Vec<u8>.
Use the .as_bytes version if you don't need ownership of the bytes.
fn main() {
let string = "foo";
println!("{:?}", string.as_bytes()); // prints [102, 111, 111]
}
BTW, The naming conventions for conversion functions are helpful in situations like these, because they allow you to know approximately what name you might be looking for.
To expand the answers above. Here are a few different conversions between types.
&str to &[u8]:
let my_string: &str = "some string";
let my_bytes: &[u8] = my_string.as_bytes();
&str to Vec<u8>:
let my_string: &str = "some string";
let my_bytes: Vec<u8> = my_string.as_bytes().to_vec();
String to &[u8]:
let my_string: String = "some string".to_owned();
let my_bytes: &[u8] = my_string.as_bytes();
String to Vec<u8>:
let my_string: String = "some string".to_owned();
let my_bytes: Vec<u8> = my_string.into_bytes();
Specifying the variable type is optional in all cases. Just added to avoid confusion.
Playground link: https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=5ad228e45a38b4f097bbbba49100ecfc
`let v1: Vec<u8> = string.encode_to_vec();`
`let v2: &[u8] = string.as_bytes();`
two work difference, in some of library use ownership of bytes !! if you use as_bytes() see compiler error: must be static.
for example: tokio_uring::fs::File::write_at()
get a ownership of bytes !!
but if you need borrowing , use as_bytes()