ActionScript 3 Language Specification

ActionScript 3.0 Language Specification > 14 Expressions > 14.9 Super expression

14.9 Super expression

SuperExpression limits the binding of a reference to a property of the base class of the current method. The value of the operand must be an instance of the current class. If Arguments is specified, its value is used as the base object of the limited reference. If no Arguments is specified, the value of this is used as the base object.

Syntax

SuperExpression may be used before a PropertyOperator in either a FullPostfixExpression or a FullNewSubexpression.

super.f(a,b,c)
super(o).f(a,b,c)

Verification

SuperExpression : super

SuperExpression : super Arguments

• Let frame be the immediately enclosing ParameterFrame
• If frame is none
  • Throw a VerificationError
• Let type be the result of typeOfThis(frame)
• Let limit be type.super
• If Arguments is specified and not empty
  • Let obj be the result verifying Arguments
  • Call verifyType(obj,limit)
• Return the type limit

Evaluation

SuperExpression : super

SuperExpression : super Arguments

• Let frame be the immediately enclosing ParameterFrame
• Let this be the value of frame.this
• Let type be the value of this.type
• Let limit be type.super
• If Arguments is empty or not specified
  • Let obj be the value of this
• Else
  • Let obj be the result of evaluating Arguments
  • If obj.type is not a subtype of limit, then throw a TypeError
• Let obj be a new instance LimitedBase(obj,limit)

Compatibility

ActionScript 2.0 supports only the first form of SuperExpression.

super.f(a,b,c)

This is equivalent to the following ActionScript 2.0 code:

this.constructor.prototype.__proto__.f.apply(this,arguments);

This differs from ActionScript 3.0 depending on the value of this, and whether the value of constructor, prototoype or __proto__ has been modified.

The second form of SuperExpression is included for future compatibility and completeness.

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