Part of the class definition:

properties : {
  test: {}
}

test: { 
  check : "String" 
}

The names of types are identical to the ones used in the API viewer:

• Boolean, String, Number, Integer, Float, Double
• Object, Array, Map
• Class, Mixin, Interface, Theme
• Error, RegExp, Function, Date, Node, Element, Document, Window, Event

test: { 
  check : "qx.core.Object"
}

Given as an array of allowed values:

test: { 
  check : [ "red", "blue", "yellow" ] 
}

The custom check method can be placed right into the property declaration:

test: { 
  check : function(value) {
    // do check...,
  }
}

By default properties are not nullable.

test: { 
  nullable : true
}

test: { 
  refine : true,
  init : "world"
}

test: { 
  event : "testChanged"
}

Explicit. A leading _apply is a preferred convention.

test: { 
  apply: "_applyTest"
}

width: { 
  apply : "_applyDimension"
},
 
height: { 
  apply : "_applyDimension"
}

Supported. Init value is recoverable using reset method.

Supported. A themeable value is stored separately and has a lower priority than the user value.

Supported. It is possible to initialize a property in the class constructor.

Supported. It is possible to enable inheritance on property level. Supports overriding, too.