Objective-C: Method Swizzling , why use class_addMethod?
0
$begingroup$
I am reviewing method-swizzling.
Why add the branch if (didAddMethod) { ?
#import <objc/runtime.h>
@implementation UIViewController (Tracking)
+ (void)load {
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
Class class = [self class];
SEL originalSelector = @selector(viewWillAppear:);
SEL swizzledSelector = @selector(xxx_viewWillAppear:);
Method originalMethod = class_getInstanceMethod(class, originalSelector);
Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector);
// When swizzling a class method, use the following:
// Class class = object_getClass((id)self);
// ...
// Method originalMethod = class_getClassMethod(class, originalSelector);
// Method swizzledMethod = class_getClassMethod(class, swizzledSelector);
BOOL didAddMethod =
class_addMethod(class,
originalSelector,
method_getImplementation(swizzledMethod),
method_getTypeEncoding(swizzledMethod));
if (didAddMethod) {
class_replaceMethod(class,
swizzledSelector,
method_getImplementation(originalMethod),
method_getTypeEncoding(originalMethod));
} else {
method_exchangeImplementations(originalMethod, swizzledMethod);
}
});
}
#pragma mark - Method Swizzling
- (void)xxx_viewWillAppear:(BOOL)animated {
[self xxx_viewWillAppear:animated];
NSLog(@"viewWillAppear: %@", self);
}
@end
Why not get Method , then method_exchangeImp ?
I take a breakpoint several times, never runs to the branch if (didAddMethod) {
objective-c objective-c-runtime
asked 13 mins ago
black_pearlblack_pearl
1135
$endgroup$
add a comment |
0
$begingroup$
I am reviewing method-swizzling.
Why add the branch if (didAddMethod) { ?
#import <objc/runtime.h>
@implementation UIViewController (Tracking)
+ (void)load {
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
Class class = [self class];
SEL originalSelector = @selector(viewWillAppear:);
SEL swizzledSelector = @selector(xxx_viewWillAppear:);
Method originalMethod = class_getInstanceMethod(class, originalSelector);
Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector);
// When swizzling a class method, use the following:
// Class class = object_getClass((id)self);
// ...
// Method originalMethod = class_getClassMethod(class, originalSelector);
// Method swizzledMethod = class_getClassMethod(class, swizzledSelector);
BOOL didAddMethod =
class_addMethod(class,
originalSelector,
method_getImplementation(swizzledMethod),
method_getTypeEncoding(swizzledMethod));
if (didAddMethod) {
class_replaceMethod(class,
swizzledSelector,
method_getImplementation(originalMethod),
method_getTypeEncoding(originalMethod));
} else {
method_exchangeImplementations(originalMethod, swizzledMethod);
}
});
}
#pragma mark - Method Swizzling
- (void)xxx_viewWillAppear:(BOOL)animated {
[self xxx_viewWillAppear:animated];
NSLog(@"viewWillAppear: %@", self);
}
@end
Why not get Method , then method_exchangeImp ?
I take a breakpoint several times, never runs to the branch if (didAddMethod) {
objective-c objective-c-runtime
asked 13 mins ago
black_pearlblack_pearl
1135
$endgroup$
$begingroup$
Unfortunately, the question is off-topic for this site. Here on CR, it is expected that the code is posted by an author or maintainer of the code, and that the poster knows why the code is written the way it is. Compare codereview.meta.stackexchange.com/a/3654/35991.
$endgroup$
– Martin R
1 min ago
$begingroup$
Your question might have an answer here on SO: stackoverflow.com/questions/34502215/….
$endgroup$
– Martin R
29 secs ago
add a comment |
0
0
0
$begingroup$
I am reviewing method-swizzling.
Why add the branch if (didAddMethod) { ?
#import <objc/runtime.h>
@implementation UIViewController (Tracking)
+ (void)load {
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
Class class = [self class];
SEL originalSelector = @selector(viewWillAppear:);
SEL swizzledSelector = @selector(xxx_viewWillAppear:);
Method originalMethod = class_getInstanceMethod(class, originalSelector);
Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector);
// When swizzling a class method, use the following:
// Class class = object_getClass((id)self);
// ...
// Method originalMethod = class_getClassMethod(class, originalSelector);
// Method swizzledMethod = class_getClassMethod(class, swizzledSelector);
BOOL didAddMethod =
class_addMethod(class,
originalSelector,
method_getImplementation(swizzledMethod),
method_getTypeEncoding(swizzledMethod));
if (didAddMethod) {
class_replaceMethod(class,
swizzledSelector,
method_getImplementation(originalMethod),
method_getTypeEncoding(originalMethod));
} else {
method_exchangeImplementations(originalMethod, swizzledMethod);
}
});
}
#pragma mark - Method Swizzling
- (void)xxx_viewWillAppear:(BOOL)animated {
[self xxx_viewWillAppear:animated];
NSLog(@"viewWillAppear: %@", self);
}
@end
Why not get Method , then method_exchangeImp ?
I take a breakpoint several times, never runs to the branch if (didAddMethod) {
objective-c objective-c-runtime
asked 13 mins ago
black_pearlblack_pearl
1135
$endgroup$
I am reviewing method-swizzling.
Why add the branch if (didAddMethod) { ?
#import <objc/runtime.h>
@implementation UIViewController (Tracking)
+ (void)load {
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
Class class = [self class];
SEL originalSelector = @selector(viewWillAppear:);
SEL swizzledSelector = @selector(xxx_viewWillAppear:);
Method originalMethod = class_getInstanceMethod(class, originalSelector);
Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector);
// When swizzling a class method, use the following:
// Class class = object_getClass((id)self);
// ...
// Method originalMethod = class_getClassMethod(class, originalSelector);
// Method swizzledMethod = class_getClassMethod(class, swizzledSelector);
BOOL didAddMethod =
class_addMethod(class,
originalSelector,
method_getImplementation(swizzledMethod),
method_getTypeEncoding(swizzledMethod));
if (didAddMethod) {
class_replaceMethod(class,
swizzledSelector,
method_getImplementation(originalMethod),
method_getTypeEncoding(originalMethod));
} else {
method_exchangeImplementations(originalMethod, swizzledMethod);
}
});
}
#pragma mark - Method Swizzling
- (void)xxx_viewWillAppear:(BOOL)animated {
[self xxx_viewWillAppear:animated];
NSLog(@"viewWillAppear: %@", self);
}
@end
Why not get Method , then method_exchangeImp ?
I take a breakpoint several times, never runs to the branch if (didAddMethod) {
objective-c objective-c-runtime
objective-c objective-c-runtime
asked 13 mins ago
black_pearlblack_pearl
1135
asked 13 mins ago
black_pearlblack_pearl
1135
asked 13 mins ago
black_pearlblack_pearl
1135
asked 13 mins ago
black_pearlblack_pearl
1135
asked 13 mins ago
black_pearlblack_pearl
1135
1135
$begingroup$
Unfortunately, the question is off-topic for this site. Here on CR, it is expected that the code is posted by an author or maintainer of the code, and that the poster knows why the code is written the way it is. Compare codereview.meta.stackexchange.com/a/3654/35991.
$endgroup$
– Martin R
1 min ago
$begingroup$
Your question might have an answer here on SO: stackoverflow.com/questions/34502215/….
$endgroup$
– Martin R
29 secs ago
add a comment |
$begingroup$
Unfortunately, the question is off-topic for this site. Here on CR, it is expected that the code is posted by an author or maintainer of the code, and that the poster knows why the code is written the way it is. Compare codereview.meta.stackexchange.com/a/3654/35991.
$endgroup$
– Martin R
1 min ago
$begingroup$
Your question might have an answer here on SO: stackoverflow.com/questions/34502215/….
$endgroup$
– Martin R
29 secs ago
$begingroup$
Unfortunately, the question is off-topic for this site. Here on CR, it is expected that the code is posted by an author or maintainer of the code, and that the poster knows why the code is written the way it is. Compare codereview.meta.stackexchange.com/a/3654/35991.
$endgroup$
– Martin R
1 min ago
$begingroup$
Unfortunately, the question is off-topic for this site. Here on CR, it is expected that the code is posted by an author or maintainer of the code, and that the poster knows why the code is written the way it is. Compare codereview.meta.stackexchange.com/a/3654/35991.
$endgroup$
– Martin R
1 min ago
$begingroup$
Your question might have an answer here on SO: stackoverflow.com/questions/34502215/….
$endgroup$
– Martin R
29 secs ago
$begingroup$
Your question might have an answer here on SO: stackoverflow.com/questions/34502215/….
$endgroup$
– Martin R
29 secs ago
add a comment |
0
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$begingroup$
Unfortunately, the question is off-topic for this site. Here on CR, it is expected that the code is posted by an author or maintainer of the code, and that the poster knows why the code is written the way it is. Compare codereview.meta.stackexchange.com/a/3654/35991.
$endgroup$
– Martin R
1 min ago
$begingroup$
Your question might have an answer here on SO: stackoverflow.com/questions/34502215/….
$endgroup$
– Martin R
29 secs ago