uCalc API Version: 2.1.3-preview.2 Released: 6/17/2026

Warning

uCalc API Preview Release Notice:The documentation describes the intended behavior of the API. The current preview build contains incomplete features, unoptimized performance, and is subject to breaking changes.

Before

Method

Product: 

String Library

Class: 

String

Creates a live, modifiable view of the substring that precedes a specified pattern match.

Syntax

Before(string, int)

Parameters

pattern
string
The pattern to find. The returned view will contain all text up to, but not including, this pattern's match.
nth
int
(Default = 1)
The 1-based occurrence of the pattern to find. For example, a value of 2 finds the second match and returns all text before it.

Return

String

A new uCalc.String object that is a live, modifiable view into the portion of the parent string that comes before the specified pattern match. Returns an empty string object if the pattern is not found or is at the beginning of the string.

Remarks

✂️ Extracting Text Before a Pattern

The Before method finds the nth occurrence of a given pattern and returns a new uCalc.String object representing all the text that precedes it. This is a fundamental tool for parsing data and is part of uCalc.String's fluent, chainable API.

Note: This method may be renamed to UpTo in a future version for better consistency with similar methods.

✨ The "Live View" Concept

The most important feature of this method is that it does not return a simple, disconnected substring. Instead, it returns a live, modifiable view into the parent string. This means:

  • Any modifications made to the child string (the returned view) will directly affect the content of the original parent string.
  • This allows for powerful, in-place editing of specific sections of a larger document without the overhead of creating and rejoining substrings.

⚙️ Parameters

  • pattern: The uCalc pattern to search for.
  • nth: A 1-based index specifying which occurrence of the pattern to find. The default value of 1 finds the first match.

Behavior on Failure

If the specified pattern is not found, or if it is found at the very beginning of the string, the method returns an empty uCalc.String object. No error is raised.

💡 Why uCalc? (Comparative Analysis)

In a standard language like C#, you would typically find the starting position of a match and then create a new substring.

C# Manual Approach:

string text = "user:admin";int colonIndex = text.IndexOf(':');if (colonIndex != -1){    string key = text.Substring(0, colonIndex);    // 'key' is now a new, disconnected string "user"}

This approach is imperative and creates disconnected data. uCalc.String provides a more powerful, declarative, and integrated solution:

The uCalc Advantage:

var s = new uCalc.String("http://example.com");var schemeView = s.Before("://"); // Returns a live view// Modifying the view changes the original string 's'schemeView.Replace("http", "https");Console.WriteLine(s); // Output: https://example.com

This ability to create live, chainable views is a key differentiator, enabling a more fluid and powerful style of text manipulation that is not possible with standard string libraries. This method is the logical counterpart to After and is often used with Between.

Examples

Extracts the key from a simple key-value pair.
				
					using uCalcSoftware;

var uc = new uCalc();
using (var s = new uCalc.String("user:admin")) {
   var key = s.Before(":");
   Console.WriteLine(key);
}
				
			
user
				
					#include <iostream>
#include "uCalc.h"

using namespace std;
using namespace uCalcSoftware;

int main() {
   uCalc uc;
   {
      uCalc::String s("user:admin");
      s.Owned(); // Causes s to be released when it goes out of scope
      auto key = s.Before(":");
      cout << key << endl;
   }
}
				
			
user
				
					Imports System
Imports uCalcSoftware
Public Module Program
   Public Sub Main()
      Dim uc As New uCalc()
      Using s As New uCalc.String("user:admin")
         Dim key = s.Before(":")
         Console.WriteLine(key)
      End Using
   End Sub
End Module
				
			
user
Chains `Before` and `Replace` to modify only the scheme of a URL, demonstrating the live view concept.
				
					using uCalcSoftware;

var uc = new uCalc();
using (var url = new uCalc.String("http://example.com")) {
   Console.WriteLine($"Original URL: {url}");
   // Get a view of the scheme part
   var schemeView = url.Before("://");
   // Modify the view
   schemeView.Replace("http", "https");
   // The original string is updated
   Console.WriteLine($"Modified URL: {url}");
}
				
			
Original URL: http://example.com
Modified URL: https://example.com
				
					#include <iostream>
#include "uCalc.h"

using namespace std;
using namespace uCalcSoftware;

int main() {
   uCalc uc;
   {
      uCalc::String url("http://example.com");
      url.Owned(); // Causes url to be released when it goes out of scope
      cout << "Original URL: " << url << endl;
      // Get a view of the scheme part
      auto schemeView = url.Before("://");
      // Modify the view
      schemeView.Replace("http", "https");
      // The original string is updated
      cout << "Modified URL: " << url << endl;
   }
}
				
			
Original URL: http://example.com
Modified URL: https://example.com
				
					Imports System
Imports uCalcSoftware
Public Module Program
   Public Sub Main()
      Dim uc As New uCalc()
      Using url As New uCalc.String("http://example.com")
         Console.WriteLine($"Original URL: {url}")
         '// Get a view of the scheme part
         Dim schemeView = url.Before("://")
         '// Modify the view
         schemeView.Replace("http", "https")
         '// The original string is updated
         Console.WriteLine($"Modified URL: {url}")
      End Using
   End Sub
End Module
				
			
Original URL: http://example.com
Modified URL: https://example.com
Internal Test: Tests edge cases for patterns that are not found or are at the start of the string.
				
					using uCalcSoftware;

var uc = new uCalc();
using (var s = new uCalc.String("A B C")) {
   
   // Case 1: Pattern is at the start. Should return an empty string.
   Console.Write("Before 'A': '");
   Console.Write(s.Before("A"));
   Console.WriteLine("'");

   // Case 2: Pattern does not exist. Should return an empty string.
   Console.Write("Before 'D': '");
   Console.Write(s.Before("D"));
   Console.WriteLine("'");

   // Case 3: Get text before the last word.
   Console.Write("Before 'C': '");
   Console.Write(s.Before("C"));
   Console.WriteLine("'");
}
				
			
Before 'A': ''
Before 'D': ''
Before 'C': 'A B '
				
					#include <iostream>
#include "uCalc.h"

using namespace std;
using namespace uCalcSoftware;

int main() {
   uCalc uc;
   {
      uCalc::String s("A B C");
      s.Owned(); // Causes s to be released when it goes out of scope

      // Case 1: Pattern is at the start. Should return an empty string.
      cout << "Before 'A': '";
      cout << s.Before("A");
      cout << "'" << endl;

      // Case 2: Pattern does not exist. Should return an empty string.
      cout << "Before 'D': '";
      cout << s.Before("D");
      cout << "'" << endl;

      // Case 3: Get text before the last word.
      cout << "Before 'C': '";
      cout << s.Before("C");
      cout << "'" << endl;
   }
}
				
			
Before 'A': ''
Before 'D': ''
Before 'C': 'A B '
				
					Imports System
Imports uCalcSoftware
Public Module Program
   Public Sub Main()
      Dim uc As New uCalc()
      Using s As New uCalc.String("A B C")
         
         '// Case 1: Pattern is at the start. Should return an empty string.
         Console.Write("Before 'A': '")
         Console.Write(s.Before("A"))
         Console.WriteLine("'")
         
         '// Case 2: Pattern does not exist. Should return an empty string.
         Console.Write("Before 'D': '")
         Console.Write(s.Before("D"))
         Console.WriteLine("'")
         
         '// Case 3: Get text before the last word.
         Console.Write("Before 'C': '")
         Console.Write(s.Before("C"))
         Console.WriteLine("'")
      End Using
   End Sub
End Module
				
			
Before 'A': ''
Before 'D': ''
Before 'C': 'A B '
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