Plist Integer and Real Number Types in JSON

Q: Plist Integer and Real Number Types in JSON

## Numeric Types in Plist Apple plist distinguishes between two numeric types: for whole numbers and for floating-point values. JSON has a single number type for both. ### Plist Example xml MaxRetries 5 Timeout 30.5 Version 3 ScaleFactor 2.0 ### JSON Output json { "MaxRetries": 5, "Timeout": 30.5, "Version": 3, "ScaleFactor": 2

Understand how Apple plist integer and real (floating-point) elements are converted to JSON numbers, and how the reverse inference works.

Basic Types

Detailed Explanation

Numeric Types in Plist

Apple plist distinguishes between two numeric types: <integer> for whole numbers and <real> for floating-point values. JSON has a single number type for both.

Plist Example

<dict>
  <key>MaxRetries</key>
  <integer>5</integer>
  <key>Timeout</key>
  <real>30.5</real>
  <key>Version</key>
  <integer>3</integer>
  <key>ScaleFactor</key>
  <real>2.0</real>
</dict>

JSON Output

{
  "MaxRetries": 5,
  "Timeout": 30.5,
  "Version": 3,
  "ScaleFactor": 2
}

Type Inference for Reverse Conversion

When converting JSON back to plist, the tool uses Number.isInteger() to decide between <integer> and <real>. A JSON value of 2.0 that JavaScript evaluates as 2 (integer) will become <integer>2</integer>. If you need <real>2.0</real>, you would need to manually adjust the output.

Large Numbers

Plist <integer> supports 64-bit signed integers (up to 9,223,372,036,854,775,807). JSON numbers are IEEE 754 double-precision floating-point, which safely represents integers up to 2^53. For very large integers, precision loss can occur during conversion.

Use Case

Essential when migrating macOS application settings that mix integer counts (retry limits, port numbers) with floating-point values (timeouts, scale factors) into JSON-based configuration systems.

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