A placeholder represents an unfinished value or the intention to create a new AST object before its concept and properties are chosen. In an editor projection, placeholder text turns missing data into an explicit call to action rather than an empty or crashing display. section 6.1.1 section 6.4
Implement placeholders by:
- Creating the new object with its concept and an initially empty settings object. section 6.1.1
- Guarding expressions that access missing settings so undefined values do not reach string or formatting functions. section 6.1.1 section 6.4
- Displaying property-specific markers such as <name> and <type>, styling them as missing, and switching to editing on click. section 6.1.1
Rental attributes
Clicking “+ attribute” adds a Data Attribute with empty settings. The projection then shows <name> and <type> until the domain expert supplies the attribute name and type. section 6.1.1 section 6.4
// (existing code:)
<div className="section">
<div><span className="keyword">attributes:</span></div>
{settings["attributes"].map((attribute, index) =>
<Projection
astObject{attribute}
ancestors={[ astObject, ...ancestors ]}
key={index}
/>
)}
// Add a button:
<button
className="add-new" #1
tabIndex={-1} #2
>+ attribute</button> #3
// (existing code again:)
</div>
The attribute-creation listing shows the event-driven step that inserts a new AST object before its editable properties are filled. section 6.1.1
