Summary - FFI
- Dart course
- Expert
- Lesson 18/47
- 5 min
Combine DynamicLibrary, lookupFunction and Pointer to write a native wrapper.
Summary: FFI
In this group we covered the core pieces of dart:ffi: dart:ffi is the C interop library, DynamicLibrary loads C libraries, lookupFunction binds native functions.
Struct represents C structs, Pointer manages memory addresses. dart:ffi works on native platforms, not on the web. In this summary you will write a native wrapper that combines all of these pieces.
Practice Summary: A NativeWrapper class
Define a NativeWrapper class with final String library; final String symbol; NativeWrapper(this.library, this.symbol); field and constructor. Add a String describe() => '$library :: $symbol'; method. In main create final w = NativeWrapper('libmylib.so', 'add');; print with print(w.describe());.
Starter code
void main() {
// define a NativeWrapper class (library, symbol; describe)
// create a NativeWrapper; print describe()
}Sample solution
class NativeWrapper {
final String library;
final String symbol;
NativeWrapper(this.library, this.symbol);
String describe() => '$library :: $symbol';
}
void main() {
final w = NativeWrapper('libmylib.so', 'add');
print(w.describe());
}Expected output
libmylib.so :: add
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What is DynamicLibrary used for?
- For UI rendering
- For garbage collection
- For loading C libraries Correct answer
- For package download
Explanation: DynamicLibrary loads C libraries.
2 Match the FFI parts
| Term | Meaning |
|---|---|
dart:ffi |
C interop |
DynamicLibrary |
Library loader |
lookupFunction |
Symbol lookup |
Pointer |
Memory address |
3 A native function symbol
final symbol = '____';
print(symbol);final symbol = 'add';
print(symbol);Explanation: 'add' is a common C function symbol.