Runtime-Computed Options

Generate dynamic, context-dependent data by referencing other field values in generator options.

Overview

Runtime-computed options allow generator parameters (like min, max, from, to) to reference other fields in the same item. This enables realistic data where values depend on each other.

Basic Usage

Reference another field using this.fieldName:

{
  "employees": {
    "count": 10,
    "item": {
      "startAge": {"gen": "number", "min": 22, "max": 35},
      "retirementAge": {
        "gen": "number",
        "min": {"ref": "this.startAge"},
        "max": 65
      }
    }
  }
}

Each employee's retirementAge will be between their startAge and 65.

Mapped References

Map referenced values to different option values:

{
  "products": {
    "count": 20,
    "item": {
      "category": {"gen": "choice", "options": ["budget", "premium", "luxury"]},
      "price": {
        "gen": "float",
        "min": {"ref": "this.category", "map": {"budget": 10, "premium": 100, "luxury": 1000}},
        "max": {"ref": "this.category", "map": {"budget": 50, "premium": 500, "luxury": 5000}},
        "decimals": 2
      }
    }
  }
}

Result:

• Budget products: $10-50
• Premium products: $100-500
• Luxury products: $1000-5000

Supported Generators

Runtime-computed options work with any generator that accepts numeric or date options:

Generator	Supported Options
number	min, max
float	min, max
date	from, to
lorem	words, sentences, paragraphs
string	length, minLength, maxLength

Common Patterns

Date Ranges

Ensure end date is after start date:

{
  "events": {
    "count": 10,
    "item": {
      "startDate": {"gen": "date", "from": "2024-01-01", "to": "2024-06-30"},
      "endDate": {
        "gen": "date",
        "from": {"ref": "this.startDate"},
        "to": "2024-12-31"
      }
    }
  }
}

Content Length by Type

{
  "articles": {
    "count": 10,
    "item": {
      "type": {"gen": "choice", "options": ["tweet", "post", "article"]},
      "content": {
        "gen": "lorem",
        "words": {"ref": "this.type", "map": {"tweet": 20, "post": 100, "article": 500}}
      }
    }
  }
}

Salary Ranges by Level

{
  "employees": {
    "count": 50,
    "item": {
      "level": {"gen": "choice", "options": ["junior", "mid", "senior", "lead"]},
      "salary": {
        "gen": "number",
        "min": {"ref": "this.level", "map": {"junior": 40000, "mid": 60000, "senior": 90000, "lead": 120000}},
        "max": {"ref": "this.level", "map": {"junior": 60000, "mid": 90000, "senior": 120000, "lead": 180000}}
      }
    }
  }
}

Important Notes

1. Field Order Matters: Referenced fields must be defined before the field that references them
2. Self-References Only: Only this.fieldName is supported (not cross-collection references)
3. Exact Map Keys: Mapping requires exact string matches for keys
4. Both Modes: Works with both eager and memory-optimized (lazy) modes
5. No Circular Dependencies: Circular references will cause errors

Limitations

• Only self-references (this.fieldName) are supported
• Cannot reference fields from other collections in options
• Map keys must exactly match the referenced field's value
• Nested field references (this.nested.field) are not supported in options

Next Steps

• Custom Generators - Create your own generators
• References - Cross-collection references
• Generators Overview - All available generators