What is FFI?
- Flutter course
- Expert
- Lesson 21/39
- 4 min
Call C libraries with dart:ffi.
What is FFI?
dart:ffi lets you call C libraries from Dart code. It binds functions written in C to Dart, providing interop; calls happen directly without bridge code.
import 'dart:ffi';
// In C: int topla(int a, int b);
typedef NativeTopla = Int32 Function(Int32 a, Int32 b);
typedef DartTopla = int Function(int a, int b);NativeFunction and typedef
You define the C function signature on the Dart side with two typedefs: one for the NativeFunction on the C side (Int32, Pointer), and one for the Dart side (int). The two types are bridged by lookupFunction.
Practice Define FFI typedefs
Define the typedefs NativeTopla = Int32 Function(Int32 a, Int32 b) and DartTopla = int Function(int a, int b). In main, print 'ffi hazir'.
Starter code
import 'dart:ffi';
// NativeTopla typedef'i tanımla (Int32 dönüşlü Function)
// DartTopla typedef'i tanımla (int dönüşlü Function)
void main() {
// 'ffi hazir' yazdır
}Sample solution
import 'dart:ffi';
typedef NativeTopla = Int32 Function(Int32 a, Int32 b);
typedef DartTopla = int Function(int a, int b);
void main() {
print('ffi hazir');
}Expected output
ffi hazir
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What does dart:ffi provide?
- Opening a database
- Calling C libraries from Dart Correct answer
- Making HTTP requests
- Drawing widgets
Explanation: dart:ffi binds C functions to Dart so they can be called directly; HTTP, widgets, or databases are not ffi's job.
2 Import dart:ffi
import 'dart:____';import 'dart:ffi';Explanation: The dart:ffi package is used for C interop; dart:io is for files/sockets, dart:async for Future/Stream, and dart:core for basic types.
3 FFI matches
| Term | Meaning |
|---|---|
dart:ffi |
C interop library |
C |
System programming language |
interop |
Cross-language bridge |
NativeFunction |
C-side signature |