I am not sure if something is wrong, or if I've missed out something VERY FUNDAMENTAL.
But I AM able to access private constructors, methods, and members of a class outside the class.
class A {
static final _a = 1;
}
void main() {
print(A._a);
}
Output:
1
Dart version:
Dart VM version: 2.8.4 (stable) (Unknown timestamp) on "linux_x64"
Screenshot of the test:
From the docs:
identifiers that start with an underscore (_) are visible only inside the library. Every Dart app is a library, even if it doesn’t use a library directive.
Private means that it's available in the file it's written in and not accessible to other files. So it's not a true private. You can read more about it here.
Related
I am working on an Android application that will call a .so file created by a different Android NDK application.
I have created the following folder structure in my project and copied over the .so files as seen below:
|--app:
|--|--src:
|--|--|--main
|--|--|--|--jniLibs
|--|--|--|--|--armeabi
|--|--|--|--|--|--libmylib.so
|--|--|--|--|--x86
|--|--|--|--|--|--libmylib.so
I call this library through my application via the following code:
static {
System.loadLibrary("mylib");
}
I then call the method from this shared object via the following code:
String str = stringFromJNI();
This does not work as the program looks for mangled function name as follows:
com.example.androidlibcall.MainActivity.stringFromJNI() where my .so function will be using a different package name and hence a different function name is generated.
I am not really sure what I need to do to call the functions from the external library, I assume I can create my own library and utilize dlopen() to load the external library and make calls to it, but was wondering if there are the other methods to achieve this or not.
My ultimate goal is to be able to create applications that can call pre-existing libraries that are on the mobile device, but since I am new to NDK/Android I am not sure what is the best method for this and have not found good examples to work with.
A lot of the pre-existing similar questions seem to be dealing with older versions of Android Studio that don't seem applicable anymore.
I am using the latest version of Android Studio (3.1.2) with Gradle 4.4 on Windows 7 machine.
Please advise.
Thanks!
Generally speaking, it's not a good idea to have native methods in application's MainActivity, but this should not worry us now that we are forging a workaround.
Assume that your new project has com.example.other.MainActivity.java, and you want to call the native method com.example.androidlibcall.MainActivity.stringFromJNI() from com.example.other.MainActivity.onCreate(). To do this, create a new Java class in your other app:
package com.example.androidlibcall;
public class MainActivity {
public static native String stringFromJNI();
}
and in your existing MainActivity class,
package com.example.other;
import static com.example.androidlibcall.MainActivity.stringFromJNI;
class MainActivity {
static {
System.loadLibrary("mylib");
}
}
public class MainActivity extends Activity {
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
…
String qq = stringFromJNI();
…
}
}
You see that com/example/androidlibcall/MainActivity.java contains no logic, no data, no code. It is only a wrapper that lets us easily use libmylib.so without rebuilding it.
Given an extension registered in gradle as foo:
class Foo {
Project proj
void setProject( Project project) {
this.proj = project
}
void setProject( String project) {
// do stuff
}
}
How do I get:
foo {
project = ':random-project'
}
to call the string setter and not fail in setProperty of the decorated extension object due to GroovyCastException?
The reason for this question arose from this issue: https://github.com/Centril/gradle-plugin-robospock/issues/5
Since I don't see any better answer yet, I am trying to suggest a possible alternative.
If you can keep type of proj as a String in Foo and where you actually use the instance of Foo class, lookup the project using the findProject method on the project object available to your plugin.
class FooPlugin implements Plugin<Project> {
// ...
void apply(Project project) {
// ...
project.findProject(fooInstance.proj)
}
}
You may find more on findProject or project methods to locate a project by path at API Documentation
There might be a way to access current Project instance in your Foo class then you may use the overloaded setter.
This works in Gradle versions 2.0 and later which is likely due to the move from Groovy 1.x to 2.x. I'd suggest using a later version of Gradle if that is possible.
Luke Daley from Gradleware informed me that this is a limitation of the Groovy language: https://issues.apache.org/jira/browse/GROOVY-2500
I've got a Visual Studio extension, where much of the functionality is written through MEF. So far, my individual functionality is per ITextBuffer, so I have used the Properties member to cache instances.
However, now I have some functionality that needs to be per-project and per-solution. The EnvDTE classes offer a Properties object but I couldn't figure out whether or not they could store my own arbitrary data. I really don't want to make my own data static.
How can I store per-project and per-solution data without having to resort to global variables?
Edit:
I might also mention that since you can't use MEF imports for static data, even if you hide it in something like a Singleton, then using the global variable route is physically impossible. So I really, really need something that is not a global.
Edit:
I'm talking about object references, not persistent values. I don't need to store anything in a solution or project file, only with the object.
I found a way to convince MEF to honour my static imports, so for now, I'm just using some static data.
(Microsoft.VisualStudio.Shell.Package.GetGlobalService(typeof(SComponentModel)) as IComponentModel).DefaultCompositionService.SatisfyImportsOnce(this);
It was posted somewhere else- maybe even on SO- took me a while to find it though. Note that this has no interface required- reflection is used, so it should be valid for any this.
If I understand your question correctly, you can create a stub class that you do the exports from, instead of trying to force your static classes to export.
public class HostClass
{
public static string StaticString
{ get { return "string value"; } }
}
public class HostClassStub
{
[Export("StaticStringValue", typeof(string))]
public string StaticString
{ get { return HostClass.StaticString; } }
}
You may also consider just making your static class un-static, if that's an option for you. Remember, that by default MEF imports are singletons, so it should be just like having a global set of variables for each project that does the import.
I know this doesn't address the VS Extensions aspect of your problem, but I haven't dealt with those. Maybe this'll give you a path to your solution, though.
I've taken a read to the Advantages of message based web services article and am wondering if there is there a recommended style/practice to versioning Restful resources in ServiceStack? The different versions could render different responses or have different input parameters in the Request DTO.
I'm leaning toward a URL type versioning (i.e /v1/movies/{Id}), but I have seen other practices that set the version in the HTTP headers (i.e Content-Type: application/vnd.company.myapp-v2).
I'm hoping a way that works with the metadata page but not so much a requirement as I've noticed simply using folder structure/ namespacing works fine when rendering routes.
For example (this doesn't render right in the metadata page but performs properly if you know the direct route/url)
/v1/movies/{id}
/v1.1/movies/{id}
Code
namespace Samples.Movies.Operations.v1_1
{
[Route("/v1.1/Movies", "GET")]
public class Movies
{
...
}
}
namespace Samples.Movies.Operations.v1
{
[Route("/v1/Movies", "GET")]
public class Movies
{
...
}
}
and corresponding services...
public class MovieService: ServiceBase<Samples.Movies.Operations.v1.Movies>
{
protected override object Run(Samples.Movies.Operations.v1.Movies request)
{
...
}
}
public class MovieService: ServiceBase<Samples.Movies.Operations.v1_1.Movies>
{
protected override object Run(Samples.Movies.Operations.v1_1.Movies request)
{
...
}
}
Try to evolve (not re-implement) existing services
For versioning, you are going to be in for a world of hurt if you try to maintain different static types for different version endpoints. We initially started down this route but as soon as you start to support your first version the development effort to maintain multiple versions of the same service explodes as you will need to either maintain manual mapping of different types which easily leaks out into having to maintain multiple parallel implementations, each coupled to a different versions type - a massive violation of DRY. This is less of an issue for dynamic languages where the same models can easily be re-used by different versions.
Take advantage of built-in versioning in serializers
My recommendation is not to explicitly version but take advantage of the versioning capabilities inside the serialization formats.
E.g: you generally don't need to worry about versioning with JSON clients as the versioning capabilities of the JSON and JSV Serializers are much more resilient.
Enhance your existing services defensively
With XML and DataContract's you can freely add and remove fields without making a breaking change. If you add IExtensibleDataObject to your response DTO's you also have a potential to access data that's not defined on the DTO. My approach to versioning is to program defensively so not to introduce a breaking change, you can verify this is the case with Integration tests using old DTOs. Here are some tips I follow:
Never change the type of an existing property - If you need it to be a different type add another property and use the old/existing one to determine the version
Program defensively realize what properties don't exist with older clients so don't make them mandatory.
Keep a single global namespace (only relevant for XML/SOAP endpoints)
I do this by using the [assembly] attribute in the AssemblyInfo.cs of each of your DTO projects:
[assembly: ContractNamespace("http://schemas.servicestack.net/types",
ClrNamespace = "MyServiceModel.DtoTypes")]
The assembly attribute saves you from manually specifying explicit namespaces on each DTO, i.e:
namespace MyServiceModel.DtoTypes {
[DataContract(Namespace="http://schemas.servicestack.net/types")]
public class Foo { .. }
}
If you want to use a different XML namespace than the default above you need to register it with:
SetConfig(new EndpointHostConfig {
WsdlServiceNamespace = "http://schemas.my.org/types"
});
Embedding Versioning in DTOs
Most of the time, if you program defensively and evolve your services gracefully you wont need to know exactly what version a specific client is using as you can infer it from the data that is populated. But in the rare cases your services needs to tweak the behavior based on the specific version of the client, you can embed version information in your DTOs.
With the first release of your DTOs you publish, you can happily create them without any thought of versioning.
class Foo {
string Name;
}
But maybe for some reason the Form/UI was changed and you no longer wanted the Client to use the ambiguous Name variable and you also wanted to track the specific version the client was using:
class Foo {
Foo() {
Version = 1;
}
int Version;
string Name;
string DisplayName;
int Age;
}
Later it was discussed in a Team meeting, DisplayName wasn't good enough and you should split them out into different fields:
class Foo {
Foo() {
Version = 2;
}
int Version;
string Name;
string DisplayName;
string FirstName;
string LastName;
DateTime? DateOfBirth;
}
So the current state is that you have 3 different client versions out, with existing calls that look like:
v1 Release:
client.Post(new Foo { Name = "Foo Bar" });
v2 Release:
client.Post(new Foo { Name="Bar", DisplayName="Foo Bar", Age=18 });
v3 Release:
client.Post(new Foo { FirstName = "Foo", LastName = "Bar",
DateOfBirth = new DateTime(1994, 01, 01) });
You can continue to handle these different versions in the same implementation (which will be using the latest v3 version of the DTOs) e.g:
class FooService : Service {
public object Post(Foo request) {
//v1:
request.Version == 0
request.Name == "Foo"
request.DisplayName == null
request.Age = 0
request.DateOfBirth = null
//v2:
request.Version == 2
request.Name == null
request.DisplayName == "Foo Bar"
request.Age = 18
request.DateOfBirth = null
//v3:
request.Version == 3
request.Name == null
request.DisplayName == null
request.FirstName == "Foo"
request.LastName == "Bar"
request.Age = 0
request.DateOfBirth = new DateTime(1994, 01, 01)
}
}
Framing the Problem
The API is the part of your system that exposes its expression. It defines the concepts and the semantics of communicating in your domain. The problem comes when you want to change what can be expressed or how it can be expressed.
There can be differences in both the method of expression and what is being expressed. The first problem tends to be differences in tokens (first and last name instead of name). The second problem is expressing different things (the ability to rename oneself).
A long-term versioning solution will need to solve both of these challenges.
Evolving an API
Evolving a service by changing the resource types is a type of implicit versioning. It uses the construction of the object to determine behavior. Its works best when there are only minor changes to the method of expression (like the names). It does not work well for more complex changes to the method of expression or changes to the change of expressiveness. Code tends to be scatter throughout.
Specific Versioning
When changes become more complex it is important to keep the logic for each version separate. Even in mythz example, he segregated the code for each version. However, the code is still mixed together in the same methods. It is very easy for code for the different versions to start collapsing on each other and it is likely to spread out. Getting rid of support for a previous version can be difficult.
Additionally, you will need to keep your old code in sync to any changes in its dependencies. If a database changes, the code supporting the old model will also need to change.
A Better Way
The best way I've found is to tackle the expression problem directly. Each time a new version of the API is released, it will be implemented on top of the new layer. This is generally easy because changes are small.
It really shines in two ways: first all the code to handle the mapping is in one spot so it is easy to understand or remove later and second it doesn't require maintenance as new APIs are developed (the Russian doll model).
The problem is when the new API is less expressive than the old API. This is a problem that will need to be solved no matter what the solution is for keeping the old version around. It just becomes clear that there is a problem and what the solution for that problem is.
The example from mythz's example in this style is:
namespace APIv3 {
class FooService : RestServiceBase<Foo> {
public object OnPost(Foo request) {
var data = repository.getData()
request.FirstName == data.firstName
request.LastName == data.lastName
request.DateOfBirth = data.dateOfBirth
}
}
}
namespace APIv2 {
class FooService : RestServiceBase<Foo> {
public object OnPost(Foo request) {
var v3Request = APIv3.FooService.OnPost(request)
request.DisplayName == v3Request.FirstName + " " + v3Request.LastName
request.Age = (new DateTime() - v3Request.DateOfBirth).years
}
}
}
namespace APIv1 {
class FooService : RestServiceBase<Foo> {
public object OnPost(Foo request) {
var v2Request = APIv2.FooService.OnPost(request)
request.Name == v2Request.DisplayName
}
}
}
Each exposed object is clear. The same mapping code still needs to be written in both styles, but in the separated style, only the mapping relevant to a type needs to be written. There is no need to explicitly map code that doesn't apply (which is just another potential source of error). The dependency of previous APIs is static when you add future APIs or change the dependency of the API layer. For example, if the data source changes then only the most recent API (version 3) needs to change in this style. In the combined style, you would need to code the changes for each of the APIs supported.
One concern in the comments was the addition of types to the code base. This is not a problem because these types are exposed externally. Providing the types explicitly in the code base makes them easy to discover and isolate in testing. It is much better for maintainability to be clear. Another benefit is that this method does not produce additional logic, but only adds additional types.
I am also trying to come with a solution for this and was thinking of doing something like the below. (Based on a lot of Googlling and StackOverflow querying so this is built on the shoulders of many others.)
First up, I don’t want to debate if the version should be in the URI or Request Header. There are pros/cons for both approaches so I think each of us need to use what meets our requirements best.
This is about how to design/architecture the Java Message Objects and the Resource Implementation classes.
So let’s get to it.
I would approach this in two steps. Minor Changes (e.g. 1.0 to 1.1) and Major Changes (e.g 1.1 to 2.0)
Approach for minor changes
So let’s say we go by the same example classes used by #mythz
Initially we have
class Foo { string Name; }
We provide access to this resource as /V1.0/fooresource/{id}
In my use case, I use JAX-RS,
#Path("/{versionid}/fooresource")
public class FooResource {
#GET
#Path( "/{id}" )
public Foo getFoo (#PathParam("versionid") String versionid, (#PathParam("id") String fooId)
{
Foo foo = new Foo();
//setters, load data from persistence, handle business logic etc
Return foo;
}
}
Now let’s say we add 2 additional properties to Foo.
class Foo {
string Name;
string DisplayName;
int Age;
}
What I do at this point is annotate the properties with a #Version annotation
class Foo {
#Version(“V1.0")string Name;
#Version(“V1.1")string DisplayName;
#Version(“V1.1")int Age;
}
Then I have a response filter that will based on the requested version, return back to the user only the properties that match that version. Note that for convenience, if there are properties that should be returned for all versions, then you just don’t annotate it and the filter will return it irrespective of the requested version
This is sort of like a mediation layer. What I have explained is a simplistic version and it can get very complicated but hope you get the idea.
Approach for Major Version
Now this can get quite complicated when there is a lot of changes been done from one version to another. That is when we need to move to 2nd option.
Option 2 is essentially to branch off the codebase and then do the changes on that code base and host both versions on different contexts. At this point we might have to refactor the code base a bit to remove version mediation complexity introduced in Approach one (i.e. make the code cleaner) This might mainly be in the filters.
Note that this is just want I am thinking and haven’t implemented it as yet and wonder if this is a good idea.
Also I was wondering if there are good mediation engines/ESB’s that could do this type of transformation without having to use filters but haven’t seen any that is as simple as using a filter. Maybe I haven’t searched enough.
Interested in knowing thoughts of others and if this solution will address the original question.
I have a custom module, Module1. In this module, I am referencing another custom module, Module2. Everything was working fine last week.
I did a fresh re-install of Orchard this morning. Since then, I have been getting this error.
None of the constructors found with 'Orchard.Environment.AutofacUtil.DynamicProxy2.ConstructorFinderWrapper' on type 'Module1' can be invoked with the available services and parameters: Cannot resolve parameter 'Module2' of constructor 'Void .ctor(...)'.
Any idea how to fix this error?
Thanks.
That means that an implementation of some interface could not be found. Several thing can have happened: a module may have failed to compile, or you forgot to make an interface derive from IDependency.
I know the post is quite old now, but just to link any possible mistake that could cause the described problem... here is my mistake.
I simply forgot to enable the referenced module from the dashboard.
Of course that didn't prevent me to add a project reference and module dependency, having the code compiling perfectly .
The point is, my referenced module doesn't contain any content type definition. It is just a module conceived to collect some functionality and common utilities. That's why I forgot to enable it.
Cheers.
You can get this error if you manually enabled your modules.
If so, fix it by deleting App_Data\cache.dat and then recycle the app pool.
I had the same issue. It seems that I referenced the concrete class and not the interface in my constructor.
public OrderService(
IRepository<Order> orderRepository,
ProductService productService,
ProductCategoryService productCategoryService
)
Instead of
public OrderService(
IRepository<Order> orderRepository,
IProductService productService,
IProductCategoryService productCategoryService
)
checklist is:
Interface derive from IDependency
Implementation derive from Interface
Constructor references the Interface
Build All and check if all referenced modules compile
Enable module in Admin panel
example:
public class myController : Controller{
private readonly IMyService _myService;
public myController(
IMyService myService
) {
_myService = myService;
}
}
public interface IMyService : IDependency
{
int GetOne();
}
public class MyService: IMyService
{
public MyService()
{ // init code }
public int GetOne()
{ return 1; }
}