UIWebView and WKWebView

Question

I want to use WKWebView for IOS8 but also need compatibility for IOS7, I have seen the posts referring to using this code:

if ([WKWebView class]) {
// do new webview stuff
}
else {
// do old webview stuff
}

But not sure what I am doing wrong as the code below gives me a linker error:

Undefined symbols for architecture i386:
"_OBJC_CLASS_$_WKWebView", referenced from:
  objc-class-ref in ViewController.o
ld: symbol(s) not found for architecture i386
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Any help much appreciated, here is my code:

.h file:

#import "WebKit/WebKit.h"
#import <UIKit/UIKit.h>
@interface ViewController : UIViewController

@property (weak, nonatomic) IBOutlet UIWebView *contentWebView;
@property (weak, nonatomic) IBOutlet WKWebView *contentWKWebView;

@end

.m file:

#import "ViewController.h"

@interface ViewController ()
@end

@implementation ViewController
@synthesize contentWebView;
@synthesize contentWKWebView;

- (void)viewDidLoad {
[super viewDidLoad];

NSString *filePath = [[NSBundle mainBundle]pathForResource:@"LockBackground" ofType:@"html"];
NSURL * fileURL = [NSURL fileURLWithPath:filePath isDirectory:NO];
NSURLRequest * myNSURLRequest = [[NSURLRequest alloc]initWithURL:fileURL];
if ([WKWebView class]) {
    [contentWKWebView loadRequest:myNSURLRequest];
} else {
    [contentWebView loadRequest:myNSURLRequest];
}
}

-(UIStatusBarStyle)preferredStatusBarStyle {
return UIStatusBarStyleLightContent;
}

- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}

@end

Answer 1

Go to your Project, click on General, scroll down to Linked Frameworks and Libraries, and add WebKit.framework as Optional. See here: Xcode 6 + iOS 8 SDK but deploy on iOS 7 (UIWebKit & WKWebKit)