从 Objective-C 类调用 Swift 方法的语法

Question

I am trying to call some code in a Utilities file written in swift from an objective-c file.

Right now the class in the swift file looks like this:

class ImageClass: NSObject {
public func imageFromString(name: String?) -> UIImage? {
//code to make image

return image
}
}

I am trying to call it from the Objective-C file with:

 UIImage *myImage = [ImageClass imageFromString:@"test"];

however this is giving error:

Use of undeclared identifier 'ImageClass'

I know the Utilities file is reachable from the Objective-C file because I call other methods there though using a shared Instance.

Can anyone suggest the proper way to call the code? I actually don't care if it's a class or through a sharedInstance, I just need to be able to call it.

Edit:

As suggested by @Charles Srstka, I CMD-clicked on the #import myapp.swift file, jumped to Definition, and it shows the following in the header:

- (UIImage * _Nullable)imageFromStringWithName:(NSString * _Nullable)name SWIFT_WARN_UNUSED_RESULT;

Accordingly, I tried adding WithName (which I'd forgotten) to the invocation so I have:

 UIImage *myImage = [ImageClass imageFromStringWithName:@"test"];

but am still getting error with or without @objc before method:

No known class method for selector 'imageFromStringWithName:'

Answer 1

In swift 4.2 and latest

1. Add this line to your "*.m" file:

    #import "YourProjectName-Swift.h"

2. Add @objc before your function:

    @objc public func imageFromString(name: String?) -> UIImage? { //code to make the image return image }

3. Call it inside Objective-C class:

    ImageClass *imgObject = [[ImageClass alloc] init]; UIImage *myImage = [imgObject imageFromStringWithName:@"test"];

Answer 2

Add this line to your Objective-C file:

#import "YourProjectName-Swift.h"

Replace YourProjectName with the name of your project. This will make all the Objective-C-compatible Swift classes in your project visible to your Objective-C code.

Note that you'll also need to add the @objc annotation to your func declataions to make the methods visible to Objective-C.