Swift实战(2)--在工程中添加object-C的类或者第三方框架

原文地址:http://stackoverflow.com/questions/24002369/how-to-call-objective-c-code-from-swift

Using Objective-C Classes in Swift

** If you have an existing class that you'd like to use, perform Step 2 and then skip to Step 5. (For some cases, I had to add an explicit 

#import <Foundation/Foundation.h

 to an older ObjC File) **

Step 1: Add Objective-C Implementation -- .m

Add a 

.m

 file to your class, and name it 

CustomObject.m

Step 2: Add Bridging Header

When adding your 

.m

 file, you'll likely be hit with a prompt that looks like this:



Click YES !

If you did not see the prompt, or accidentally deleted your bridging header, add a new 

.h

 file to your project and name it 

<#YourProjectName#>-Bridging-Header.h  and reference it from your build settings

 

Step 3: Add Objective-C Header -- .h

Add another 

.h

 file and name it 

CustomObject.h

Step 4: Build your Objective-C Class

In 

CustomObject.h

#import <Foundation/Foundation.h>

@interface CustomObject : NSObject

@property (strong, nonatomic) id someProperty;

- (void) someMethod;

@end

In 

CustomObject.m

#import "CustomObject.h"

@implementation CustomObject

- (void) someMethod {
NSLog(@"SomeMethod Ran");
}

@end

Step 5: Add Class to Bridging-Header

In 

YourProject-Bridging-Header.h

:

#import "CustomObject.h"

Step 6: Use your Object

In 

SomeSwiftFile.swift

:

var instanceOfCustomObject: CustomObject = CustomObject()
instanceOfCustomObject.someProperty = "Hello World"
println(instanceOfCustomObject.someProperty)
instanceOfCustomObject.someMethod()

No need to import explicitly, that's what the bridging header is for.

Using Swift Classes in Objective-C

Step 1: Create New Swift Class

Add a 

.swift

 file to your project, and name it 

MySwiftObject.swift

In 

MySwiftObject.swift

:

import Foundation

class MySwiftObject : NSObject {

var someProperty: AnyObject = "Some Initializer Val"

init() {}

func someFunction(someArg:AnyObject) -> String {
var returnVal = "You sent me \(someArg)"
return returnVal
}

}

Step 2: Import Swift Files to ObjC Class

In 

SomeRandomClass.m

:

#import "<#YourProjectName#>-Swift.h"

The file:

<#YourProjectName#>-Swift.h

 should already be created automatically in your project, even if you can not see it.

Step 3: Use your class

MySwiftObject * myOb = [MySwiftObject new];
NSLog(@"MyOb.someProperty: %@", myOb.someProperty);
myOb.someProperty = @"Hello World";
NSLog(@"MyOb.someProperty: %@", myOb.someProperty);
NSString * retString = [myOb someFunction:@"Arg"];
NSLog(@"RetString: %@", retString);

Using PURE Swift Classes in Objective-C

As pointed out by @TomášLinhart in the comments, "To be accessible and usable in Objective-C, a Swift class must be a descendant of an Objective-C class or it must be marked 

@objc

." Because our first example is a descendant of 

NSObject

, the compiler does this automatically. Let's look at an example class that is not a desce
b532
ndant of an Objective-C Class.

Step 1: Create New Swift Class

Add a 

.swift

 file to your project, and name it 

PureSwiftObject.swift

In 

PureSwiftObject.swift

:

import Foundation

// Note '@objc' prefix
@objc class PureSwiftObject {

var name: String
init(name: String) {
self.name = name
}

// Needed to add a class level initializer
class func newInstanceNamed(name: String) -> PureSwiftObject {
return PureSwiftObject(name: name)
}

// Just a method for demonstration
func someMethod() {
println("Some method ran in pure swift object")
}
}

For this, I create a class initializer called 'newInstanceNamed:'. Because this class is no longer a descendent of 

NSObject

, it no longer has access to 'alloc' or 'new'. Perhaps there is another workaround, but this is the only way that I have found. I didn't find any explicit mention of this in the docs. If you do, and it contradicts my approach, please tell me and I'll update the answer to conform to the suggested style.

Step 2: Import Swift Files to ObjC Class

In 

SomeRandomClass.m

:

#import "<#YourProjectName#>-Swift.h"

(if you haven't already done so)

Step 3: Use your pure swift class

PureSwiftObject * pureSwiftObject = [PureSwiftObject newInstanceNamed:@"Janet"];
NSLog(@"PureSwiftNamed: %@", pureSwiftObject.name);
[pureSwiftObject someMethod];

Note:

1. CodeCompletion wasn't behaving as accurately as I'd like it to. On my system, running a quick build w/ "cmd + r" seemed to help Swift find some of the Objc code and vice versa.

2. If you add 

.swift

 file to an older project and get error: 

dyld: Library not loaded: @rpath/libswift_stdlib_core.dylib

, try completely