Added info about nullptr and connect() style

CONTRIBUTING.md

@@ -14,7 +14,12 @@ Note that cutter is still under development and many parts of the code are to be
 
 ### CutterCore class
 
-This is the main class where every link with r2 is made. It is *unique* accross the whole process. To access it, simply call `CutterCore::getInstance()`.
+This is the main class where every link with r2 is made. It is *unique* accross the whole process. To access it, simply call `Core()`.
+
+Example:
+```c++
+Core()->getOffset();
+```
 
 ### Calling a radare2 command
 
@@ -22,10 +27,20 @@ There are two ways to do it:
 * `CutterCore::cmd()` *(Discouraged)* Only use it for commands which yells no output
 * `CutterCore::cmdj()` To be used with json commands like `cmdj("agj")` or `cmdj("aflj")`. It is way easier to parse a json output.
 
+Example:
+```c++
+QJsonArray array = Core()->cmdj("pdj 1 @ main").array();
+```
+
 ### Seek the current file
 
 To modify radare2 seek use `CutterCore::seek(const RVA offset)`. This is important because it will emit a `CutterCore::seekChanged(RVA offset)` signal.
-Never ever call cmd("s offset");
+Never ever call `cmd("s offset")`;
+
+Example:
+```c++
+Core()->seek(0xdeadbeef);
+```
 
 ### Creating a widget
 
@@ -33,7 +48,7 @@ Make sure to connect the `CutterCore::seekChanged(RVA offset)` signal so your wi
 
 ## General coding guidelines
 
-### Code formatting
+### Coding style
 
 We follow [these guidelines](https://wiki.qt.io/Qt_Coding_Style) to format the code.
 If in doubt, you can use [AStyle 2.06](https://sourceforge.net/projects/astyle/files/astyle/astyle%202.06/) to format the code. The command line for formatting the code according to the style is:
@@ -42,6 +57,32 @@ If in doubt, you can use [AStyle 2.06](https://sourceforge.net/projects/astyle/f
 astyle --project=src/Cutter.astylerc src/filename.cpp
 ```
 
+#### Loops
+
+We use C++11 foreach loop style which means any "foreach" loop should look like:
+```c++
+for (QJsonValue value : importsArray) {
+    doSomething(value);
+}
+```
+
+#### Nullptr
+
+Please do not use `0` nor `Q_NULLPTR`, only use `nullptr`.
+
+Example:
+```c++
+QObject *object = nullptr;
+```
+
+#### Connecting signals
+
+To connect a signal to a slot, this is the preferred way to do it:
+```c++
+connect(sender, &QObject::destroyed, this, &MyObject::objectDestroyed);
+```
+The main reason is that this syntax allows the use of lambda functions.
+
 ### Functions documentation
 
 It's good to add some documentation to your functions when needed. To do so we follow these [rules](http://doc.qt.io/qt-5/qdoc-guide-writing.html).