Actions have three responsibilities.
- execution + supporting methods
- to specify the target object
- event publishing
Our programming model could provide several syntaxes to put these responsibilities in different places. It already supports two (standard actions, and mixins).
Standard syntax
The standard syntax uses regular methods on the target object. Naming conventions are used to associate the action with supporting methods (default, choices, hide, disable and validate):
public class Customer {
public Customer placeOrder(Product p, int quantity) { ... }
public boolean hidePlaceOrder() { return this.isBlackListed(); }
public String disablePlaceOrder() { return clockService.outsideShoppingHours(); }
public String disable1PlaceOrder(Product p) { return p.isOutOfStock() ? "Out of stock": null; } // could also hide parameters similarly
public Collection<Product> choices0PlaceOrder() { ... } // or autoComplete0PlaceOrder(String search) { ... }
public Product default0PlaceOrder() { return orderService.findLastProductPurchasedBy(this); }
public int default1PlaceOrder() { return 1; }
public String validate1PlaceOrder(int quantity) { return quantity <= 0 ? "Can only order +ve amounts": null; }
public String validatePlaceOrder(Product p, int quantity) { return catalogService.runningLowOn(p) && quantity > 4 ? "We're running low on that product, no more than 4" : null; }
}Mixins syntax
Parameters syntax (proposed)
Per this thread on slack, we could introduce a Parameters object (in Java 14+, this might be a record) to bring together all of the parameters into a single object. This would make it easier to avoid issues with numbering etc.
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