In Oracle APEX templates, special characters like the open bracket { have specific functions as part of substitution and directive syntax. However, there are times when you need to display an actual open bracket character in your template output rather than trigger APEX’s template processing. Escaping the open bracket correctly ensures that your content renders as intended without being interpreted as part of the template language. This blog will guide you through the proper methods to escape open brackets within Oracle APEX templates, helping you maintain accurate display and avoid syntax errors.
When working with templates, it is possible to encounter a situation where the open bracket { can be confused for the start of a directive (e.g., {if} or {loop}). This issue arises when the open bracket appears in the middle of the code, followed by a directive, causing a potential conflict. To avoid this confusion, you can escape the open bracket using the syntax {{/}.
In this tutorial, we will walk you through how and when to use the escape sequence {{/} in APEX templates, and provide examples to demonstrate its usage.
1. Why Do You Need to Escape the Open Bracket {?
The APEX templating engine uses brackets { and } to define directives, such as {if}, {loop}, {case}, etc. In some cases, when an open bracket is placed before these directives on the same line, it might be misinterpreted as the start of a directive, causing a parsing error.
Escape Sequence:
{{/}: The escape sequence to use when you need to display an open bracket { in the template text without it being interpreted as the start of a directive.
2. When Do You Need to Escape the Open Bracket {?
You need to escape the { when it appears before a directive in a line, causing the template engine to interpret it as part of a directive. For example:
{if VAL/}&VAL.{else/}unknown{endif/}
In the above case, if you want to include { literally (e.g., in a mathematical expression), the APEX engine will interpret it as the start of a directive. To avoid this, use the escape sequence {{/} to display the { symbol literally.
3. Example 1: Escaping the Open Bracket in a Mathematical Expression
Scenario:
You want to display coordinates such as {c, d}, but without the template engine interpreting { as the start of a directive.
Without escaping:
<span>The coordinates {c, d} = {if VAL/}&VAL.{else/}unknown{endif/}</span>
This could cause an error because the APEX engine might think {c, d} is part of a directive. To prevent this issue, you should escape the { by using the escape sequence {{/}.
Escaped version:
<span>The coordinates {{/}c, d} = {if VAL/}&VAL.{else/}unknown{endif/}</span>
Explanation:
{{/}c, d}: This ensures the { character is displayed literally and not treated as part of a directive.
The rest of the expression {if VAL/}&VAL.{else/}unknown{endif/} works as expected and shows either the value of VAL or unknown.
Expected Output:
If VAL is set to 10, the output will be:
The coordinates {c, d} = 10
If VAL is not set, it will display:
The coordinates {c, d} = unknown
4. Example 2: No Need to Escape Brackets in Simple Cases
In many cases, you won’t need to escape the open bracket {. If the { is simply part of your content and not followed by a directive on the same line, it will be treated as a regular character.
Scenario:
You want to display {c, d} in a regular expression or a descriptive sentence.
<span>The coordinates { c, d } = {if VAL/}&VAL.{else/}unknown{endif/}</span>
Explanation:
Here, the { c, d } part is simply text and doesn’t conflict with any directives.
The rest of the template will work as usual, displaying either the value of VAL or unknown.
Expected Output:
If VAL is set to 20, the output will be:
The coordinates { c, d } = 20
If VAL is not set, it will display:
The coordinates { c, d } = unknown
5. Example 3: Escaping Brackets When Using Directives
In some situations, the bracket { might appear in combination with a directive, and you need to escape it to prevent conflicts. Here's an example where you need to escape the open bracket before using an if directive.
Scenario:
You want to display an expression such as {c, d} = 10 only if a certain condition is true.
Without escaping:
<span>{c, d} = {if VAL/}&VAL.{else/}unknown{endif/}</span>
This could cause a parsing error, so you should use {{/} to escape the {.
Escaped version:
<span>{{/}c, d} = {if VAL/}&VAL.{else/}unknown{endif/}</span>
Expected Output:
If VAL is set to 10, the output will be:
{c, d} = 10
If VAL is not set, it will display:
{c, d} = unknown
6. Example 4: No Need to Escape Inside Block Directives
If you are using a block directive, such as {if} or {loop}, where the brackets {} appear inside the block, you don’t need to escape them. For instance:
{if VAL/}
<span>The coordinates {c, d} = {VAL}</span>
{else/}
<span>The coordinates {c, d} = unknown</span>
{endif/}
This will work perfectly fine because the {c, d} part is outside of the directive, and APEX doesn’t interpret the brackets as part of the directive.
7. Summary of When to Escape the Open Bracket
Escape Bracket: Use {{/} when you want to display { literally in a context where the APEX engine might interpret it as the start of a directive. This typically happens when an open bracket { is immediately followed by a directive, such as {if}, {loop}, or others.
No Escape Needed: You don't need to escape { when it’s simply part of the content (i.e., not immediately followed by a directive).
8. Best Practices
Be aware of directive boundaries: If you’re working with template expressions or custom formatting, always ensure that the { is not interpreted as part of a directive. If it’s in a context where it might be, use the escape sequence.
Use escaping sparingly: Only escape { when necessary. Overusing it can make your templates harder to read.
Mastering how to escape open brackets in Oracle APEX templates is essential for creating flexible and robust templates, especially when dealing with custom HTML or code snippets. By applying the correct escape sequences or alternative encoding techniques, you ensure that your templates show literal brackets exactly where needed, preserving the visual and functional integrity of your application. Proper escaping not only prevents processing conflicts but also enhances template maintainability and readability.
