In Dart the trim(), trimLeft() and trimRight() string methods do not take a parameter to specify unwanted non-whitespace characters.
What is the best way to trim a specific character from the ends of a string in Dart?
I am using this for now, but it feels hard to remember and not very generic:
final trailing = RegExp(r"/+$");
final trimmed = "test///".replaceAll(trailing, "");
assert(trimmed == "test");
There is no specific functionality to trim non-whitespace from the end of a string.
Your RegExp based approach is reasonable, but can be dangerous when the character you want to remove is meaningful in a RegExp.
I'd just make my own function:
String removeTrailing(String pattern, String from) {
if (pattern.isEmpty) return from;
var i = from.length;
while (from.startsWith(pattern, i - pattern.length)) i -= pattern.length;
return from.substring(0, i);
}
Then you can use it as:
final trimmed = removeTrailing("/", "test///")
assert(trimmed == "test");
The corresponding trimLeading function would be:
String trimLeading(String pattern, String from) {
if (pattern.isEmpty) return from;
var i = 0;
while (from.startsWith(pattern, i)) i += pattern.length;
return from.substring(i);
}
Since the existing answer by lrn has a lot of problems - including infinite loop scenarios - I thought I'd post my version.
String trimLeft(String from, String pattern){
if( (from??'').isEmpty || (pattern??'').isEmpty || pattern.length>from.length ) return from;
while( from.startsWith(pattern) ){
from = from.substring(pattern.length);
}
return from;
}
String trimRight(String from, String pattern){
if( (from??'').isEmpty || (pattern??'').isEmpty || pattern.length>from.length ) return from;
while( from.endsWith(pattern) ){
from = from.substring(0, from.length-pattern.length);
}
return from;
}
String trim(String from, String pattern){
return trimLeft(trimRight(from, pattern), pattern);
}
To trim all trailing/right characters by specified characters, use the method:
class StringUtil {
static String trimLastCharacters(String srcStr, String pattern) {
if (srcStr.length > 0) {
if (srcStr.endsWith(pattern)) {
final v = srcStr.substring(0, srcStr.length - 1 - pattern.length);
return trimLastCharacters(v, pattern);
}
return srcStr;
}
return srcStr;
}
}
For example, you want to remove all 0 behind the decimals
$23.67890000
then, invoke the method
StringUtil.trimLastCharacters("$23.67890000", "0")
finally, got the output:
$23.6789
Related
I'm getting an error in this code:
void main() {
List<String> wave(String str) {
List<String> results = [];
String newStr;
int i = 0;
for (String ltr in str.split('')) {
newStr = str;
if (ltr != ' ') {
newStr[i] = ltr.toUpperCase();
results.add(newStr);
}
i++;
}
return results;
}
print(wave(' gap '));
}
the error is at the line:
newStr[i] = ltr.toUpperCase;
Despite when I try print(newStr[i]); I don't get an error and the code is executed correctly!
In Dart String operation, operator[] returns a string. Which means, array[index] is used for getting the string in the index position. That is why you're getting that error, because you can't set at specific index using this operator[] in dart. See the documentation for details.
To replace at the specific index in dart, you can use replaceFirst(Pattern from, String to, [int startIndex = 0]) as the other answer mentioned. Or, you can use substring(int start, [int? end]) as follows:
if (ltr != ' ' && i < newStr.length) {
newStr = newStr.substring(0, i) + ltr.toUpperCase() + newStr.substring(i+1);
results.add(newStr);
}
To make the code bug free, I've added the checking of the value of i in it. You should add the checking to avoid out of bound access.
try to replace
newStr[i] = ltr.toUpperCase();
to
newStr = newStr.replaceFirst(ltr,ltr.toUpperCase(),i);
So the result will be [ Gap , gAp , gaP ]
Honestly, I don't know how char is defined in Dart, but I think accessing index of String is kind of getter, thus cannot be set to a new value.
I have a simple exercise in Coderbyte, it just want to have a function that's WordSplit(strArr) read the array of strings stored in strArr, For example I have two elements like ["hellocat", "apple,bat,cat,goodbye,hello,yellow,why"]
I just want to to determine if the first element in the input can be split into two words, where both words exist in the dictionary that is provided in the second input.
For example: the first element can be split into two words: hello and cat because both of those words are in the dictionary.
So the program should return the two words that exist in the dictionary separated by a comma, as this result hello,cat .
I've made a recursive solution below. It checks if the string to be split starts with any word in the dictionary. If it exists, the function is called again using a substring with that first word removed.
This function only works up to the first word that isn't in the dictionary since you did not specify the expected behavior when the inputted word is not made up of words in the dictionary. You could make it throw an exception perhaps, but please specify your expectation.
void main() {
print(wordSplit(["hellocat", "apple,bat,cat,goodbye,hello,yellow,why"]));
//hello,cat
}
String wordSplit(List<String> arg) {
String wordToSplit = arg[0];
String dict = arg[1];
List<String> parsedDict = arg[1].split(',');
for(String word in parsedDict) {
if(wordToSplit.startsWith(word)) {
//If the substring would be empty, don't do more recursion
if(word.length == wordToSplit.length) {
return word;
}
return word + ',' + wordSplit([wordToSplit.substring(word.length), dict]);
}
}
return wordToSplit;
}
#include <bits/stdc++.h>
using namespace std;
vector<string> converToWords(string dict) {
vector<string> res;
string s = "";
int n = dict.length();
for(int i=0; i<n; i++) {
if(dict[i] == ',') {
res.push_back(s);
s = "";
}
else s += dict[i];
}
res.push_back(s);
s = "";
return res;
}
string solve(string str[]) {
string result = "";
string word = str[0], dict = str[1];
int n = word.length();
vector<string> vs = converToWords(dict);
unordered_set<string> ust;
for(auto it: vs) ust.insert(it);
// for(auto i=ust.begin(); i!=ust.end(); i++){
// cout<<*i<<endl;
// }
string s = "";
for(int i=0; i<n; i++) {
s += word[i];
// cout<<s<<endl;
string temp = word.substr(i+1, n-(i+1));
// cout<<temp<<endl;
if(ust.find(s) != ust.end() && ust.find(temp) != ust.end()) {
cout<<s<<endl;
cout<<temp<<endl;
result += s+","+temp;
break;
}
temp = "";
}
return result;
}
int main() {
string arr[2];
cin>>arr[0]>>arr[1];
cout << solve(arr);
return 0;
}
I want to put each word in a string into a separate string. So if my string has a list of words like, "John, Mary, Barbara" and the words are separate by a carriage return (not a comma as shown in the example), how do I put John into one string, Mary into another string and Barbara into a third string. The strings are not created so I will have to create them on the fly and that is ok. This is what I have tried:
for (n; n<100; n++){
s1 = s[n:n]
if(s1 == "\n") {
break
}
}
Since I want this separation to occur for every object (a specific column in a module) I will have to put whatever the correct code is into a loop like "for o in m do{ }.
Thank you for helping me.
Maybe these functions would help. However, you would have to get familiar with the Skip type (the DXL manual helps with that).
stringSplit() divides str into substrings based on a delimiter, returning an array (Skip type) of these substrings. If pattern is a String, then its contents are used as the delimiter when splitting str. If pattern is empty or null, the value of a single space is used. If pattern is a single space, str is split on whitespace, with leading whitespace and runs of contiguous whitespace characters ignored.
Skip stringSplit(string str, string pattern) {
if (null str) return null
if (null(pattern) || 0 == length(pattern))
pattern = " ";
Skip result = create;
int i = 0; // index for searching in str
int j = 0; // index counter for result array
bool found = true;
while (found) {
// find pattern
int pos = 0;
int len = 0;
found = findPlainText(str[i:], pattern, pos, len, true);
if (found) {
// insert into result
put(result, j++, str[i:i+pos-1]);
i += pos + len;
}
}
// append the rest after last found pattern
put(result, j, str[i:]);
return result;
}
You might prefer to remove the commas first since the last word is not followed by a comma.
stringWipe() returns a copy of str with all occurrences of characters in chars eliminated:
string stringWipe(string str, string chars) {
if (null str) return str
int lenStr = length str
if (lenStr == 0) return str
int lenChars = length(chars);
if (lenChars == 0) return str
Buffer buf = create
int i
for (i=0; i<lenStr; i++) {
char c = str[i]
bool skip = false
int j
for (j=0; j<lenChars; j++) {
if (c == chars[j]) {
skip = true
break
}
}
if (skip)
continue
buf += c
}
string result = stringOf(buf);
delete buf
return result
}
Is there a way to split a string by some symbol but only at first occurrence?
Example: date: '2019:04:01' should be split into date and '2019:04:01'
It could also look like this date:'2019:04:01' or this date : '2019:04:01' and should still be split into date and '2019:04:01'
string.split(':');
I tried using the split() method. But it doesn't have a limit attribute or something like that.
You were never going to be able to do all of that, including trimming whitespace, with the split command. You will have to do it yourself. Here's one way:
String s = "date : '2019:04:01'";
int idx = s.indexOf(":");
List parts = [s.substring(0,idx).trim(), s.substring(idx+1).trim()];
You can split the string, skip the first item of the list created and re-join them to a string.
In your case it would be something like:
var str = "date: '2019:04:01'";
var parts = str.split(':');
var prefix = parts[0].trim(); // prefix: "date"
var date = parts.sublist(1).join(':').trim(); // date: "'2019:04:01'"
The trim methods remove any unneccessary whitespaces around the first colon.
Just use the split method on the string. It accepts a delimiter/separator/pattern to split the text by. It returns a list of values separated by the provided delimiter/separator/pattern.
Usage:
const str = 'date: 2019:04:01';
final values = string.split(': '); // Notice the whitespace after colon
Output:
Inspired by python, I've wrote this utility function to support string split with an optionally maximum number of splits. Usage:
split("a=b=c", "="); // ["a", "b", "c"]
split("a=b=c", "=", max: 1); // ["a", "b=c"]
split("",""); // [""] (edge case where separator is empty)
split("a=", "="); // ["a", ""]
split("=", "="); // ["", ""]
split("date: '2019:04:01'", ":", max: 1) // ["date", " '2019:04:01'"] (as asked in question)
Define this function in your code:
List<String> split(String string, String separator, {int max = 0}) {
var result = List<String>();
if (separator.isEmpty) {
result.add(string);
return result;
}
while (true) {
var index = string.indexOf(separator, 0);
if (index == -1 || (max > 0 && result.length >= max)) {
result.add(string);
break;
}
result.add(string.substring(0, index));
string = string.substring(index + separator.length);
}
return result;
}
Online demo: https://dartpad.dev/e9a5a8a5ff803092c76a26d6721bfaf4
I found that very simple by removing the first item and "join" the rest of the List
String date = "date:'2019:04:01'";
List<String> dateParts = date.split(":");
List<String> wantedParts = [dateParts.removeAt(0),dateParts.join(":")];
Use RegExp
string.split(RegExp(r":\s*(?=')"));
Note the use of a raw string (a string prefixed with r)
\s* matches zero or more whitespace character
(?=') matches ' without including itself
You can use extensions and use this one for separating text for the RichText/TextSpan use cases:
extension StringExtension on String {
List<String> controlledSplit(
String separator, {
int max = 1,
bool includeSeparator = false,
}) {
String string = this;
List<String> result = [];
if (separator.isEmpty) {
result.add(string);
return result;
}
while (true) {
var index = string.indexOf(separator, 0);
print(index);
if (index == -1 || (max > 0 && result.length >= max)) {
result.add(string);
break;
}
result.add(string.substring(0, index));
if (includeSeparator) {
result.add(separator);
}
string = string.substring(index + separator.length);
}
return result;
}
}
Then you can just reference this as a method for any string through that extension:
void main() {
String mainString = 'Here was john and john was here';
print(mainString.controlledSplit('john', max:1, includeSeparator:true));
}
Just convert list to string and search
productModel.tagsList.toString().contains(filterText.toLowerCase())
What I'm trying to do is to make it where the user can type in a textbox and then click on a button and it will search the richtextbox for what they are looking for and if it found something it will change the label.
(Instances)
`
Button = btn_Search
Textbox = InputBox
RichTextBox = rtb
Label = Results`
Use this method, to find any Text inside your RichTextBox.
public int FindMyText(string searchText, int searchStart, int searchEnd)
{
// Initialize the return value to false by default.
int returnValue = -1;
// Ensure that a search string and a valid starting point are specified.
if (searchText.Length > 0 && searchStart >= 0)
{
// Ensure that a valid ending value is provided.
if (searchEnd > searchStart || searchEnd == -1)
{
// Obtain the location of the search string in richTextBox1.
int indexToText = richTextBox1.Find(searchText, searchStart, searchEnd, RichTextBoxFinds.MatchCase);
// Determine whether the text was found in richTextBox1.
if(indexToText >= 0)
{
// Return the index to the specified search text.
returnValue = indexToText;
}
}
}
return returnValue;
}
call this method like this:
var res= FindMyText("hello",0. richTextBox1.Text.Length);
now if res>-1, that means positive match, then you can set your labels i.e.
if(res>-1){
lbl1.Text = "hello found";
}
source here and here
Another method of searching text that is far more clean is as below,but first you need to add
System.Text.RegularExpressions namespace to your project;
private void SearchButton_Click(object sender, EventArgs e)
{
if (textBox1.TextLength >= 1)
{
string word = textBox1.Text;//The text you want to search.
Regex searchterm = new Regex(word);//A Regular Expression is most efficient way of working with text.
MatchCollection matches = searchterm.Matches(richTextBox1.Text);
if (matches.Count >= 1)
{
Results=matches.Count.ToString();//Your label to display match instances.
richTextBox1.SelectAll();
richTextBox1.SelectionBackColor = Color.White;
richTextBox1.DeselectAll();
foreach (Match match in matches)
{
richTextBox1.Select(match.Index, match.Length);
richTextBox1.SelectionBackColor = Color.Orange;
richTextBox1.DeselectAll();
}
}
}
}
This should do the job,furthermore if you want to specify additional search options,replace the line with Regex searchterm with anyone below,
Case Insensitive
Regex searchterm = new Regex(word,RegexOptions.IgnoreCase);
Whole Word Search
Regex searchterm = new Regex(#"\b"+word+"\b");
Case Insensitive and Whole Word Search
Regex searchterm = new Regex(#"\b"+word+"\b",RegexOptions.IgnoreCase);
and one more thing,Regex searches are case-sensitive by default.