Laur IVAN

Initialize a Typescript Interface with JSON

TL;DR: You can initialise a typescript interface using JSON objects. On my quest to load and save objects as JSON, I found that you can convert a JSON object to an interface via something called type assertion. Basically, if you have an interface:

export interface PathInterface {
  path: string
  enabled: boolean  
}

export interface PathInterface {

path: string

enabled: boolean

}

you can load a JSON object via JSON.parse(json) straight to an instantiation of the interface. Then, you can use the said instantiation in e.g. a component. Now, all is nice, but what if you want to initialise an instance of the PathInterface interface? That’s simple. You…read more

Aug.01

Mock an Observable Interface

Posted by laur in Software, Tutorial

TL;DR: Use a doAnswer() with a new Answer<Observable<Type>>() if you have to mock observables. Today I wrote my first test where I had to mock an observable interface:

public interface UserDatabase {
    Observable<User> readUser(String username);
}

public interface UserDatabase {

Observable<User> readUser(String username);

}

where the User model is:

public class User {
    private String name;
    private String password;

    public User(String name, String password) {
        this.name = name;
        this.password = password;
    }

    public String getName() {
        return name;
    }

    public String getPassword() {
        return password;
    }
}

public class User {

private String name;

private String password;

public User(String name, String password) {

this.name = name;

this.password = password;

}

public String getName() {

return name;

}

public String getPassword() {

return password;

}

Solution In my test class (named UserDatabaseTest), I first mocked the interface:

@Mock
UserDatabase mockUserDatabase;

1 2	@Mock UserDatabase mockUserDatabase;

` Then, my setup() method is:

@Before
public void setup() {
    MockitoAnnotations.initMocks(this);

    // Mock one user answer
    doAnswer(new Answer<Observable<User>>() {
        @Override
        public Observable<User> answer(InvocationOnMock invocation) throws Throwable {
            return Observable.just(user);
        }
    }).when(mockUserDatabase).readUser(USER_NAME);
}

@Before

public void setup() {

MockitoAnnotations.initMocks(this);

// Mock one user answer

doAnswer(new Answer<Observable<User>>() {

@Override

public Observable<User> answer(InvocationOnMock invocation) throws Throwable {

return Observable.just(user);

}

}).when(mockUserDatabase).readUser(USER_NAME);

}

where USER_NAME is a String. To use it, you need to attach an observer and assert:

@Test
public void canGetUser() {
    Observable<User> userObservable = mockUserDatabase.readUser(UserCommon.USER_NAME);

    TestObserver<User> userTestObserver = new TestObserver<>();
    userObservable.subscribe(userTestObserver);

    userTestObserver.assertReceivedOnNext(Collections.singletonList(user));
}

@Test

public void canGetUser() {

Observable<User> userObservable = mockUserDatabase.readUser(UserCommon.USER_NAME);

TestObserver<User> userTestObserver = new TestObserver<>();

userObservable.subscribe(userTestObserver);

userTestObserver.assertReceivedOnNext(Collections.singletonList(user));

}

This is quite simple. Alternative Note: This I haven’t tried yet, but here it goes… If you want…read more

Feb.14

GoogleApiClient .connect() Interface or Class

Posted by laur in Software

TL;DR: If it’s your code, check the version play services ( com.google.android.gms:play-services-*). If you’re using a library, check if the library has a version using play services >= 8.1.0. If not, you’ll need to clone and upgrade it yourself. The other day I got an interesting error coming out when running an app: ‘GoogleApiClient.connect()‘ was expected to be of type interface but was found to be virtual The reason was a backwards incompatible change in 8.1.0 where GoogleApiClient changed its signature. Moreover, it was in a library using version 7.x while…read more

Oct.19

TIL: Lambda Expressions

Posted by laur in Software

TL;DR: A lambda expression is a shortcut notation to anonymous inner classes containing a single method. Usually, they define implementations for functional interfaces (interfaces declaring a single method). Today I finally found out what lambda expressions are (formally) by watching this tutorial. Lambda expressions are a concise way of passing pieces of code around. You can look at lambda expressions as shorthand for anonymous inner classes. There is a catch though: They are valid for functional interfaces. Functional interfaces Functional interfaces are interfaces defining a single method, like this:

interface IFunctional {
    void method1();
}

interface IFunctional {

void method1();

}

Mar.10

Use a Java Enum with Strings

Posted by laur in Software

In my project I wanted to log messages using predefined categories. Traditionally, I do it via classes (if the messages are specific to the functions provided by that class):

public class LogWrapper {
    public static final String EVENT_ERROR = "Error";
    public static final String EVENT_LOAD = "Load";

    // ...
};

public class LogWrapper {

public static final String EVENT_ERROR = "Error";

public static final String EVENT_LOAD = "Load";

// ...

};

or an interface (pretty much the same thing):

public interface LogEvents {
    String EVENT_ERROR = "Error";
    String EVENT_LOAD = "Load";
};

public interface LogEvents {

String EVENT_ERROR = "Error";

String EVENT_LOAD = "Load";

};

These solutions are prone to errors (e.g. when performing copy-paste and forgetting to change the string), so I wondered if there is an enum-based approach. Of course there is:

public enum LogEvents{
    EVENT_ERROR("Error"),
    EVENT_LOAD("Load"),
    EVENT_OK("OK");


    private String value;

    LogEvents(final String value) {
        this.value = value;
    }

    public String getValue() {
        return value;
    }

    @Override
    public String toString() {
        return this.getValue();
    }
}

public enum LogEvents{

EVENT_ERROR("Error"),

EVENT_LOAD("Load"),

EVENT_OK("OK");

private String value;

LogEvents(final String value) {

this.value = value;

}

public String getValue() {

return value;

}

@Override

public String toString() {

return this.getValue();

}

Quite nice, but more verbose than the interface variant (and also prone to the copy-paste duplication). That’s why I ended up…read more