iOS 开发·备战 2022 金三银四 -runtime 原理与实践: 消息转发详解篇

objc_msgSend(id _Nullable self, SEL _Nonnull op, ...)`

[array insertObject:foo atIndex:5];

objc_msgSend(array, @selector(insertObject:atIndex:), foo, 5);

void fooMethod(id obj, SEL _cmd)  {    NSLog(@"Doing foo");}
+ (BOOL)resolveInstanceMethod:(SEL)aSEL{    if(aSEL == @selector(foo:)){        class_addMethod([self class], aSEL, (IMP)fooMethod, "v@:");        return YES;    }    return [super resolveInstanceMethod];}

- (id)forwardingTargetForSelector:(SEL)aSelector {    if(aSelector == @selector(foo:)){        return [[BackupClass alloc] init];    }    return [super forwardingTargetForSelector:aSelector];}

- (void)forwardInvocation:(NSInvocation *)invocation {    SEL sel = invocation.selector;    if([alternateObject respondsToSelector:sel]) {        [invocation invokeWithTarget:alternateObject];    } else {        [self doesNotRecognizeSelector:sel];    }}
- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector {    NSMethodSignature *methodSignature = [super methodSignatureForSelector:aSelector];    if (!methodSignature) {        methodSignature = [NSMethodSignature signatureWithObjCTypes:"v@:*"];    }    return methodSignature;}

-(NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector{    if (aSelector==@selector(run)) {        return [NSMethodSignature signatureWithObjCTypes:"v@:"];    }    return [super methodSignatureForSelector: aSelector];}
-(void)forwardInvocation:(NSInvocation *)anInvocation{    SEL selector =[anInvocation selector];
    RunPerson *RP1=[RunPerson new];    RunPerson *RP2=[RunPerson new];
    if ([RP1 respondsToSelector:selector]) {
        [anInvocation invokeWithTarget:RP1];    }    if ([RP2 respondsToSelector:selector]) {
        [anInvocation invokeWithTarget:RP2];    }    }

- (void)viewDidLoad {    [super viewDidLoad];    [self.view setBackgroundColor:[UIColor whiteColor]];    self.title = @"Test2ViewController";
    //实例化一个button,未实现其方法    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];    button.frame = CGRectMake(50, 100, 200, 100);    button.backgroundColor = [UIColor blueColor];    [button setTitle:@"消息转发" forState:UIControlStateNormal];    [button addTarget:self               action:@selector(doSomething)     forControlEvents:UIControlEventTouchUpInside];    [self.view addSubview:button];}

#import "NSObject+CrashLogHandle.h"
@implementation NSObject (CrashLogHandle)
- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector {    //方法签名    return [NSMethodSignature signatureWithObjCTypes:"v@:@"];}
- (void)forwardInvocation:(NSInvocation *)anInvocation {    NSLog(@"NSObject+CrashLogHandle---在类:%@中 未实现该方法:%@",NSStringFromClass([anInvocation.target class]),NSStringFromSelector(anInvocation.selector));}
@end

if ([object respondsToSelector: @selector(selectorName)]) {    //using new API} else {    //using deprecated API}

if (NSClassFromString(@"ClassName")) {        //using new API}else {    //using deprecated API}

#define isOperatingSystemAtLeastVersion(majorVersion, minorVersion, patchVersion)[[NSProcessInfo processInfo] isOperatingSystemAtLeastVersion: (NSOperatingSystemVersion) {    majorVersion,    minorVersion,    patchVersion}]
if (isOperatingSystemAtLeastVersion(11, 0, 0)) {    //using new API} else {    //using deprecated API}

- (void)viewDidLoad {    [super viewDidLoad];    [self.view setBackgroundColor:[UIColor whiteColor]];    self.title = @"Test3ViewController";
    UITableView *tableView = [[UITableView alloc] initWithFrame:CGRectMake(0, 64, 375, 600) style:UITableViewStylePlain];    tableView.delegate = self;    tableView.dataSource = self;    tableView.backgroundColor = [UIColor orangeColor];
    // May Crash Line    tableView.contentInsetAdjustmentBehavior = UIScrollViewContentInsetAdjustmentNever;
    [tableView registerClass:[UITableViewCell class] forCellReuseIdentifier:@"UITableViewCell"];    [self.view addSubview:tableView];}

if (isOperatingSystemAtLeastVersion(11, 0, 0)) {    scrollView.contentInsetAdjustmentBehavior = UIScrollViewContentInsetAdjustmentNever;} else {    viewController.automaticallyAdjustsScrollViewInsets = NO;}

#import "UIScrollView+Forwarding.h"#import "NSObject+AdapterViewController.h"
@implementation UIScrollView (Forwarding)
- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector { // 1
    NSMethodSignature *signature = nil;    if (aSelector == @selector(setContentInsetAdjustmentBehavior:)) {        signature = [UIViewController instanceMethodSignatureForSelector:@selector(setAutomaticallyAdjustsScrollViewInsets:)];    }else {        signature = [super methodSignatureForSelector:aSelector];    }    return signature;}
- (void)forwardInvocation:(NSInvocation *)anInvocation { // 2
    BOOL automaticallyAdjustsScrollViewInsets  = NO;    UIViewController *topmostViewController = [self cm_topmostViewController];    NSInvocation *viewControllerInvocation = [NSInvocation invocationWithMethodSignature:anInvocation.methodSignature]; // 3    [viewControllerInvocation setTarget:topmostViewController];    [viewControllerInvocation setSelector:@selector(setAutomaticallyAdjustsScrollViewInsets:)];    [viewControllerInvocation setArgument:&automaticallyAdjustsScrollViewInsets atIndex:2]; // 4    [viewControllerInvocation invokeWithTarget:topmostViewController]; // 5}
@end

#import "NSObject+AdapterViewController.h"
@implementation NSObject (AdapterViewController)
- (UIViewController *)cm_topmostViewController {    UIViewController *resultVC;    resultVC = [self cm_topViewController:[[UIApplication sharedApplication].keyWindow rootViewController]];    while (resultVC.presentedViewController) {        resultVC = [self cm_topViewController:resultVC.presentedViewController];    }    return resultVC;}
- (UIViewController *)cm_topViewController:(UIViewController *)vc {    if ([vc isKindOfClass:[UINavigationController class]]) {        return [self cm_topViewController:[(UINavigationController *)vc topViewController]];    } else if ([vc isKindOfClass:[UITabBarController class]]) {        return [self cm_topViewController:[(UITabBarController *)vc selectedViewController]];    } else {        return vc;    }}
@end