Manipulate paste content in WKWebView

Question

I need to manipulate the text that is pasted into a WKWebView (from any source) running an asynchronous operation that can take some time.

My original idea was to use Ja

Answer 1

FOR POSTERITY:

I'm sure there a way to do this using JS exists and is cleaner but I managed to achieve the result using method swizzling:

//Method Swizzling
UIView *webContentView = self.webView.contentView;
if(webContentView != nil)
{
    //Paste:
    NSError *error;
    [webContentView swizzleMethod:@selector(paste:) withSelector:@selector(my_paste:) error:&error];
    if(error != nil)
    {
        NSLog("Failed to swizzle 'paste:' into WKContentView: %@, error);
        NSAssert(false, error);
    }

    ...
}

Where the contentView is:

- (UIView *)contentView
{
    return [self subviewWithClassName:@"WKContentView"];
}

The method my_paste: need to be part of UIResponder (that is implemented by the private WKContentView)

#pragma mark - Method Swizzling UIResponder

@interface UIResponder (WebComposerSwizzling)

- (void)my_paste:(id)sender;
#define original_paste my_paste

@end

@implementation UIResponder (WebComposerSwizzling)

- (void)my_paste:(id)sender
{
    MailComposerViewController* strongComposer = sCurrentComposer;
    if (strongComposer)
        [strongComposer manipulatePasteboard:nil];
    [self original_paste:sender];
}

@end

Note that sCurrentComposer is a static variable in my ViewController

__weak MailComposerViewController* sCurrentComposer;

---

The various utilities:

UIView+SubviewSearch

import UIKit

extension UIView {

    /// Find a subview corresponding to the className parameter, recursively.
    @objc public func subviewWithClassName(_ className: String) -> UIView? {
        if NSStringFromClass(type(of: self)) == className {
            return self
        } else {
            for subview in subviews {
                return subview.subviewWithClassName(className)
            }
        }
        return nil
    }
}

NSObject+Swizzling

import Foundation

extension NSObject {

    enum NSObjectSwizzlingError: Error {
        case originalSelectorNotFound
    }

    @objc public func swizzleMethod(_ currentSelector: Selector, withSelector newSelector: Selector) throws {
        if let currentMethod = self.instanceMethod(for: currentSelector),
            let newMethod = self.instanceMethod(for:newSelector) {
            method_exchangeImplementations(currentMethod, newMethod)
        } else {
            throw NSObjectSwizzlingError.originalSelectorNotFound
        }
    }

    @objc public func instanceMethod(for selector: Selector) -> Method? {
        let classType: AnyClass! = object_getClass(self)
        return class_getInstanceMethod(classType, selector)
    }
}

(I'm sorry about the Swift <> OBJ-C mix)