Summary - dart:ffi
- Flutter course
- Expert
- Lesson 25/39
- 4 min
Combine DynamicLibrary and lookupFunction to call C.
Summary - dart:ffi
Calling a C function combines two steps: load the library with DynamicLibrary.open, and bind the function to Dart with lookupFunction. Define the signatures with two typedefs (Native and Dart).
final lib = DynamicLibrary.open('libmath.so');
final topla = lib.lookupFunction<NativeTopla, DartTopla>('topla');
print(topla(2, 3));Practice Call the abs function
First define the typedefs NativeAbs = Int32 Function(Int32) and DartAbs = int Function(int). In main, get lib with DynamicLibrary.process(), look up the 'abs' symbol with lookupFunction, and print the result of abs(-5).
Starter code
import 'dart:ffi';
// NativeAbs ve DartAbs typedef'lerini tanımla (Int32/int Function(Int32/int))
void main() {
// Süreç kütüphanesini al
// lookupFunction ile abs sembolünü ara
// negatif bir sayıyı mutlak değere çevirip yazdır
}Sample solution
import 'dart:ffi';
typedef NativeAbs = Int32 Function(Int32);
typedef DartAbs = int Function(int);
void main() {
final lib = DynamicLibrary.process();
final abs = lib.lookupFunction<NativeAbs, DartAbs>('abs');
print(abs(-5));
}Expected output
5
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Which two ffi tools combine to call a C function?
- setState and build
- DynamicLibrary and lookupFunction Correct answer
- Widget and BuildContext
- Navigator and Route
Explanation: DynamicLibrary loads the C library, lookupFunction converts the symbol to a Dart function; together they let you call the C function.
2 Call the topla function
print(____(2, 3));print(topla(2, 3));Explanation: The Dart function returned by lookupFunction is called by its variable name; lib is the library, and call and run are not valid call syntax.
3 dart:ffi summary matches
| Term | Meaning |
|---|---|
dart:ffi |
FFI framework |
DynamicLibrary |
Library object |
lookupFunction |
Symbol binding |
typedef |
Signature definition |