Hybrid programming in Apple System development (2): Mutual invocation of Swift and C

When making calls between Swift and C, it is necessary to first understand the type conversion relationship between the two languages:

C type	Swift type
bool	CBo OL
Char, signed char	cchar
unsigned char	CUNSIGNEDCH Ar
short	CShort
unsigned short	cunsignedshort
int	CInt
unsigned int	cunsignedint
long	clong
unsigned long	cunsignedlong
Long long	clonglong
unsigned long long	cunsignedlonglong
wchar_t	Cwidechar
char16_t	CChar16
char32_t	CCHA R32
float	cfloat
double	cdouble

Let's start by demonstrating how to invoke the C method in swift and create a swift project: Create a C code file in the project: This time you will be prompted to generate the bridging Header, select Create.

After the creation of the file, the code structure is as follows, you can see a file named:< project name >-bridging-header.h, this is the bridge between Swift and C file.

In the configuration of the project you can see that the bridge file is specified here, so if you forget to create this file, do not worry, you can specify a new one here.

Code to implement C: MyCFile.h

Mycfile.c

The introduction of the C code in the bridge file header file, very simple, directly import a bit can be.

You can then call the C method directly in the Swift file:

Here we add some code to implement the two point: A, C code in the SWIFT code call two, data transfer (in the case of strings) MyCFile.h

c The call to the Swift method is actually equivalent to registering a global function pointer, which can be found in the definition of swiftcallbackfun.

There are some OC syntax in this: the ^ operator, which indicates that this is a closure, that is, the functions in Block,swift are delivered in the form of closures. __nonnull indicates that the object should not be empty, because at the time of mixing, the Swift compiler does not know whether a Objective-c object is optional or non-optional, so the Xcode 6.3 Introduces a new feature of objective-c: nullability annotations, which can be defined as __nullable or __nonnull. MYCFILE.C here is a callback to the Swift method.

Main.swift

The code in Swift has two points to note: First, the way in which incoming strings in C are processed in swift. Assign a value to the global callback first, so that you can call the method from C to Swift.

Hybrid programming in Apple System development (2): Mutual invocation of Swift and C