How to deal with template taking std::function as arguments?

[egolearner]

    template <typename T>
    void set_filter(T &&func) {
       // ...
    }

T's receiver is std::function<bool(uint64_t)>.

We tried to add the following mapping info

        infoMap.put(new Info("std::function<bool(uint64_t)>").pointerTypes("FilterFunction"));
        infoMap.put(new Info("SomeClass::set_filter<std::function<bool(uint64_t)> >&&").javaNames("setFiler"));

mvn install works but the function is omitted from generated java file.

[saudet]

There isn't a way to map that as a "basic container", yet, but if it's just for an argument, we can map it using a FunctionPointer, as is done in many presets, for example, here: https://github.com/bytedeco/javacpp-presets/blob/master/pytorch/src/main/java/org/bytedeco/pytorch/presets/torch.java#L995

[egolearner]

        infoMap.put(new Info("std::function<bool(uint64_t)>").pointerTypes("FilterFunction"));

    public static class FilterFunction extends FunctionPointer {
        static { Loader.load(); }
        /** Pointer cast constructor. Invokes {@link Pointer#Pointer(Pointer)}. */
        public    FilterFunction(Pointer p) { super(p); }
        protected FilterFunction() { allocate(); }
        private native void allocate();
        public native boolean call(@Cast("uint64_t") long key);
    }

Hi @saudet, I added FilterFunction definition according to your comments. It worked if I add another non template function.

  void set_filter2 (std::function<bool(uint64_t)> &&func) {
    filter_ = std::move(func);
  }

However, the original function is a template function. I still cannot get it work. I have tried adding the following mapping info.

//        infoMap.put(new Info("SomeClass::set_filter<std::function<bool(uint64_t)> >&&").javaNames("set_filter"));


//        infoMap.put(new Info("SomeClass::set_filter<std::function<bool(uint64_t)> >&&")
//                .javaText("public native void set_filter(@ByVal FilterFunction func);"));

[saudet]

Try without the &&, it's not being processed as part of type signature, although it probably should...

[egolearner]

Remove && works. Thanks a lot @saudet

        infoMap.put(new Info("SomeClass::set_filter<std::function<bool(uint64_t)> >").javaNames("set_filter"));

[saudet]

BTW, I've added support for std::function as a "basic container" in commit https://github.com/bytedeco/javacpp/commit/587ed7a4e704927eb9238f0fae80ff9a5d546ed7, so this should work now. Please give it a try with the snapshots: http://bytedeco.org/builds/

[egolearner]

Got stuck with the following mvn error. Help needed.

[ERROR] Plugin org.bytedeco:javacpp:javacpp-1.5.8-SNAPSHOT or one of its dependencies could not be resolved: Could not find artifact org.bytedeco:javacpp:jar:javacpp-1.5.8-SNAPSHOT in sonatype-nexus-snapshots (https://oss.sonatype.org/content/repositories/snapshots) -> [Help 1]

[saudet]

It's clearly here: https://oss.sonatype.org/content/repositories/snapshots/org/bytedeco/javacpp/1.5.8-SNAPSHOT/

[saudet]

In any case, it's easy to build from source, so just do that if you're not able to fix whatever networking issue you're having.

[egolearner]

got mvn problem solved.

Am I supposed to add the following mapping info?

infoMap.put(new Info("std::function<bool(uint64_t)>").pointerTypes("FunctionPointer"));

Parsing phase succeeds with the following warning

[WARNING] Method "public native void com.mycompany.MyClass.set_filter(org.bytedeco.javacpp.FunctionPointer)" has an abstract FunctionPointer parameter, but a concrete subclass is required. Compilation will most likely fail.

And building fails with the following message

Execution javacpp-compiler of goal org.bytedeco:javacpp:1.5.8-SNAPSHOT:build failed: 1
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:215)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:156)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:148)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:117)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:81)
    at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build (SingleThreadedBuilder.java:56)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:128)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:305)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:192)
    at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:105)
    at org.apache.maven.cli.MavenCli.execute (MavenCli.java:957)
    at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:289)
    at org.apache.maven.cli.MavenCli.main (MavenCli.java:193)
    at sun.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:498)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:282)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:225)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:406)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:347)
Caused by: org.apache.maven.plugin.PluginExecutionException: Execution javacpp-compiler of goal org.bytedeco:javacpp:1.5.8-SNAPSHOT:build failed: 1
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:148)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:210)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:156)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:148)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:117)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:81)
    at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build (SingleThreadedBuilder.java:56)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:128)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:305)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:192)
    at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:105)
    at org.apache.maven.cli.MavenCli.execute (MavenCli.java:957)
    at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:289)
    at org.apache.maven.cli.MavenCli.main (MavenCli.java:193)
    at sun.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:498)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:282)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:225)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:406)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:347)
Caused by: java.lang.ArrayIndexOutOfBoundsException: 1
    at org.bytedeco.javacpp.tools.Generator.classes (Generator.java:1550)
    at org.bytedeco.javacpp.tools.Generator.generate (Generator.java:246)
    at org.bytedeco.javacpp.tools.Builder.generateAndCompile (Builder.java:580)
    at org.bytedeco.javacpp.tools.Builder.build (Builder.java:1167)
    at org.bytedeco.javacpp.tools.BuildMojo.execute (BuildMojo.java:417)
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:137)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:210)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:156)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:148)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:117)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:81)
    at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build (SingleThreadedBuilder.java:56)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:128)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:305)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:192)
    at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:105)
    at org.apache.maven.cli.MavenCli.execute (MavenCli.java:957)
    at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:289)
    at org.apache.maven.cli.MavenCli.main (MavenCli.java:193)
    at sun.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:498)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:282)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:225)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:406)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:347)

[saudet]

You'll need to use another name than "FunctionPointer".

[egolearner]

You'll need to use another name than "FunctionPointer".

Still not work.

        infoMap.put(new Info("std::function<bool(uint64_t)>").pointerTypes("MyFilterFunction"));

cannot find symbol

[ERROR] symbol: class MyFilterFunction

48:  public native void set(@ByRef(true) MyFilterFunction func);

[saudet]

Info.define needs to be set: https://github.com/bytedeco/javacpp/wiki/Mapping-Recipes#defining-wrappers-for-basic-c-containers

[egolearner]

It works. I appreciate your effort @saudet

[saudet]

This has now been released with JavaCPP 1.5.8. Enjoy!