IBInspectable Typing

ID

swift.ibinspectable_typing

Severity

low

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Reliability

Language

Swift

Tags

ios, reliability, suspicious-code, ui

Description

Reports an @IBInspectable property whose declared type is not in the set Interface Builder can encode and present in the Attributes inspector. The compiler accepts any type on an @IBInspectable property, but only a fixed list of scalar types are wired through to the design-time inspector. Anything else silently fails to appear, leaving the property unsettable from the storyboard.

The supported types are:

  • Int, CGFloat, Double, Float

  • Bool, String

  • CGPoint, CGSize, CGRect

  • UIColor, NSColor, UIImage, NSImage

Their T? / Optional<T> forms are also acceptable.

@IBInspectable var x: Int = 0                  // OK
@IBInspectable var c: UIColor?                 // OK
@IBInspectable var arr: [Int] = []             // FLAW
@IBInspectable var dict: [String: Int] = [:]   // FLAW
@IBInspectable var custom: MyType?             // FLAW

Rationale

Marking a property @IBInspectable is a contract: the value will be editable from the storyboard. Using an unsupported type breaks that contract silently. The property compiles and the storyboard wiring appears to succeed, but the value never reaches the runtime.

Remediation

Use one of the supported scalar types, or expose a supported-typed property that adapts to your richer model.

// Instead of an array, expose the canonical scalar:
@IBInspectable var cornerRadius: CGFloat = 0

// Instead of a custom struct, expose its components:
@IBInspectable var shadowColor: UIColor = .black
@IBInspectable var shadowOffsetX: CGFloat = 0
@IBInspectable var shadowOffsetY: CGFloat = 0

References