1. Open your project on the Kuika platform.
2. Select the project you want to work on from the Apps screen.
3. Open the relevant screen in the UI Design module.
4. Click on the + ADD ACTION menu in the Properties panel on the right side.

5. From the + ADD ACTION menu, add the String > Substring action according to the trigger event you want (Initial Actions, OnClick, OnBlur, etc.).
6. Fill in the following fields in the settings panel that opens:

• Value: The full text from which the subtitle will be extracted.
• Starting Index: The position where the subtitle will start (0-based indexing).
• Count: The number of characters to be included in the subtitle.

These fields can be linked to fixed values, form inputs, or action results via the Symbol Picker.

In a registration form, you want to take the first 3 letters of the name entered by the user and generate a user code.

Scenario flow:

• The user enters “John” in the fullname field.
• In the Substring action:
  
  • Value: FormComponent.fullname
  • Starting Index: 0
  • Count: 3
• The action result returns “Joh”.
• This value can be used to generate the user ID: ID-Joh-2025

• Dynamic Start: The start index can be determined based on the position of a character in the text (e.g., after the @ character).
• Conditional Subtext: If the text length exceeds a certain value, only the first X characters can be taken.
• Substring + Concat Combination: The part obtained with Substring can be combined with another text to create new values (e.g., username + ID).

Technical Risks

• Invalid Index Error: Make sure that the Starting Index and Count values do not exceed the length of the text. Otherwise, the system may return an error or an empty value.
• Use of Negative Values: Negative indexes are not supported. Values must be zero or positive.
• Empty or Undefined Text: If the Value field is empty or null, the action will not execute. The text should be checked for validity beforehand.
• Type Mismatch: Entering text in fields that expect numbers (or vice versa) may cause unexpected errors in the system.
• Language and Character Support: Special characters or multi-byte characters (e.g., emojis, Turkish characters) may be counted as more characters than expected in some systems. Compatibility testing is recommended.

Substring is an ideal, powerful, and flexible action for managing and organizing text-based operations in your applications by breaking them into parts. It is frequently used in scenarios such as form validation, username generation, and content filtering.