NativeScript / NativeScript/android
Enable generation of default (0-arguments) constructor when extending classes
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- C++
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Description
If the developer extends a base class with no default constructor, they have no way of explicitly specifying that they want a default constructor code to be generated in Java. This is a certain limitation if the class needs to be declared in the AndroidManifest and is instantiated by the system (attempting to use IntentService is one such case - Android will attempt to create an instance of the implementation of IntentService, but will crash, as it tries to invoke a default constructor, which the developer cannot declare).
Given the following Java class:
package a.b;
public class Base {
public Base(String a) { ... }
}
and the following implementation in JavaScript:
a.b.Base.extend("a.b.ExtendedBase", {
init: function() {
_this("arbitrary string");
// -> will introduce additional logic in the sole ctor block
// in Java, but will not create an additional constructor
}
});
will output
package a.b;
@com.tns.JavaScriptImplementation(javaScriptFile = "./ExtendedBase.js")
public class ExtendedBase extends a.b.Base implements com.tns.NativeScriptHashCodeProvider {
/* No default constructor */
public ExtendedBase (java.lang.String param_0){
super(param_0);
/*
Additional logic to handle more arguments -> a result of the init function
*/
com.tns.Runtime.initInstance(this);
}
public boolean equals__super(java.lang.Object other) {
return super.equals(other);
}
public int hashCode__super() {
return super.hashCode();
}
}
Developers have no way to declare a default constructor for a.b.ExtendedBase.
Instead what I need is
package a.b;
@com.tns.JavaScriptImplementation(javaScriptFile = "./ExtendedBase.js")
public class ExtendedBase extends a.b.Base implements com.tns.NativeScriptHashCodeProvider {
/* default constructor */
public ExtendedBase () {
this("Arbitrary String");
}
public ExtendedBase (java.lang.String param_0){
super(param_0);
/*
Additional logic to handle more arguments -> a result of the init function
*/
com.tns.Runtime.initInstance(this);
}
}
Generating custom constructors based on the javascript code will require additional analysis, and may not be worth looking into at the moment.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
The issue provides JavaScript and Java examples but names no source file, test, or entry point. Begin by locating the constructor-generation path for class extensions; done means an extension of a base class without a no-argument constructor can expose a generated zero-argument constructor that delegates as specified, with coverage for the shown case.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- android, cpp, java, javascript
- Domain
- mobile, tooling
- Issue type
- Feature
- Difficulty
- 5/5
- Estimated time
- Over a week
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 30/100