I need to make the SDK for one of my project, What I need to do is make a search class which return the response from the web API,
I'm looking for something like this.
SearchController * sc = [[SearchController alloc] initWithSearchText:#"google"];
This method is called every time, when I change the textField text, and the response I get should be in block.
Any help and reference would be appreciated.
SearchController.h
typedef void (^SearchHandler)(id results,NSError *error);
#interface SearchController : NSObject
{
SearchHandler searchBlock;
}
-(void)searchWithText:(NSString *)strText Results:(SearchHandler)searchResult;
SearchController.m
-(void)searchWithText:(NSString *)strText Results:(SearchHandler)searchResult
{
searchBlock = [searchResult copy];
//call api for text search
}
-(void)getResponseOfApi
{
//code where get api response
searchBlock(apiResonse,apiError);
}
call SearchController api with block
SearchController * sc = [[SearchController alloc] init];
[sc searchWithText:#"google" Results:^(id results, NSError *error) {
//block with api response
}];
You can make one block method in your SearchController and get response of type you want.
-(void)executeSearchRequestWithHandler:(void (^)(BOOL result))completionHandler {
//Do your api calling and than handle completionHandler
completionHandler(YES);
//You can set completionHandler type that you want like NSArray,NSString,NSDictionary etc
}
Now call this method like this.
[sc executeSearchRequestWithHandler:^(BOOL result) {
if (result) {
}
}];
Note: Here I have created block with BOOL parameter, you can set parameter type you want from response like NSArray,NSDictionary,NSString etc.
Related
I'm learning to develop iOS applications and now I'm reading some Objective-C source code.
This is a method to get user profile.
+ (void)getProfile:(void (^)(NSString *message))completion {
NSDictionary *dic = #{#"module":#"profile"};
[[self defaultManager] POST:KBaseUrl parameters:dic success:^(AFHTTPRequestOperation *operation, id responseObject) {
if ([self jsonOKForResponseObject:responseObject] && [self checkLogin:responseObject]) {
[ProfileManager sharedInstance].rank = responseObject[#"Variables"][#"space"][#"group"][#"grouptitle"];
[ProfileManager sharedInstance].credit = responseObject[#"Variables"][#"space"][#"credits"];
[ProfileManager sharedInstance].gender = responseObject[#"Variables"][#"space"][#"gender"];
completion(nil);
} else {
completion(#"fail");
}
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
completion(#"fail");
}];
}
My question is about the completion block.
I suppose that the completion block returns void and receives an NSString parameter.
In the block, what does completion(nil) mean?
Does that mean the block completion calls it self and send nil as parameter?
Doesn't that conflict with the parameter's type NSString*?
I'm not quite familiar with block in ObjC. Can anyone give a hint?
Yes you are right. It calls itself and sends nil as a parameter and it doesn't conflict with the NSString parameter. You are just passing nil to the NSString param.
You can call the above method like:
[YourClass getProfile:^(NSString *message) {
//message will be nill if you pass completion(nil);
}];
So when you pass the nill in the completion block, the message in the above method call will be nil!
The completion block is to notify you that your method call is complete, and at this point you can let that method pass certain paramteres , and if we consider your method:
+ (void)getProfile:(void (^)(NSString *message))completion {
NSDictionary *dic = #{#"module":#"profile"};
[[self defaultManager] POST:KBaseUrl parameters:dic success:^(AFHTTPRequestOperation *operation, id responseObject) {
if ([self jsonOKForResponseObject:responseObject] && [self checkLogin:responseObject]) {
.....
completion(#"hey sucess");
} else {
completion(#"if loop failed");
}
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
completion(#"some error occured");
}];
}
and when you call the method getProfile:
[YourClass getProfile:^(NSString *message) {
//Execution will reach here when the method call for getPRofile is complete and you have a result which you just sent through the completion block as a parameter which is a string and is waiting for you to process.
//you can do more from here
if([message isEqualToString:#"hey success"]){
//do something
}
if([message isEqualToString:#"if loop failed"]){
//do something
}
if([message isEqualToString:#"some error occured"]){
//do something
}
}];
As per #rmaddy comment, iis always a good practice to use BOOL to indicate the status success or fail rather than depending on a string as string can get localized/changed. We shold use the string to get more description of the error.
So your block should be:
+ (void)getProfile:(void (^)(BOOL status,NSString *message))completion {
.....
completion(YES,#"hey success");
}
and you can call it like":
[YourClass getProfile:^(BOOL status, NSString *message) {
if(status){
//get the success message
}else{
//get the fail message
}
}];
Blocks had a lot of type like :-
As a local variable:
returnType (^blockName)(parameterTypes) = ^returnType(parameters) {...};
As a property:
#property (nonatomic, copy, nullability) returnType (^blockName)(parameterTypes);
As a method parameter:
- (void)someMethodThatTakesABlock:(returnType (^nullability)(parameterTypes))blockName;
As an argument to a method call:
[someObject someMethodThatTakesABlock:^returnType (parameters) {...}];
As a typedef:
typedef returnType (^TypeName)(parameterTypes);
TypeName blockName = ^returnType(parameters) {...};
read more about it from here
Completion block does not return anything. It is just a piece of code to be executed, thats all. Though, you can give it some input where you call it so you can use the result elsewhere.
NSString *message is the input for your block so when you call your function getProfile as:
[MyClass getProfile:^(NSString *message) {
// write code to be executed when getProfile function finishes its job and sends message here.
}];
[MyClass getProfile:nil];
When used like this you're preferring not to do anything when getProfile finishes its job.
You are probably mixing your network manager's function's completion block with the one you wrote.
I am facing app extension close issues , please tell me if anyone know what wrong am doing.I am using action extension after preform some action inside extension i need to return response back.
Sample Code
// With Success Case
- (void) completeActionWithItems: (NSString *) response {
NSExtensionItem *extensionItem = [[NSExtensionItem alloc] init];
extensionItem.attachments = #[[[NSItemProvider alloc] response typeIdentifier: (NSString *)kUTTypePlainText]];
[self.extensionContext completeRequestReturningItems: #[extensionItem] completionHandler: nil];
}
// With Error Case
- (void) completeActionWithError: (NSError *) error {
[self.extensionContext cancelRequestWithError: error];
}
With Success Case working fine but some time is not closing,
With Error Case not working above code.
Please let me know what went wrong.Thanks
When you create an action extension, this is the default method which will close the Action Extension View Controller:
- (IBAction)done {
// Return any edited content to the host app.
// This template doesn't do anything, so we just echo the passed in items.
[self.extensionContext completeRequestReturningItems:self.extensionContext.inputItems completionHandler:nil];
}
Since this method is already provided, you should just try calling it from your success method.
// With Success Case
- (void) completeActionWithItems: (NSString *) response {
NSExtensionItem *extensionItem = [[NSExtensionItem alloc] init];
extensionItem.attachments = #[[[NSItemProvider alloc] response typeIdentifier: (NSString *)kUTTypePlainText]];
[self.extensionContext completeRequestReturningItems: #[extensionItem] completionHandler: nil];
// Call to "done" method
[self done];
}
I'm working on a simple instagram project now.
for several occasions I've encountered the same problem.
To work with instagram I use InstagramKit Engine. It has some preset (void)s to make life easier. However I'm always stuck at the same problem.
Let's say we've got this:
- (void)getSelfUserDetails
{
[[InstagramEngine sharedEngine] getSelfUserDetailsWithSuccess:^(InstagramUser *userDetail) {
NSLog(#"%#",userDetail);
} failure:^(NSError *error) {
}];
}
Here userDetail is used inside of the "Success". And it works nice. What I need is to somehow save it after the block is done.
I've tried several things from creating a property to store the userDetails up to making my own method to return the userDetails. The same trouble with saving ints, NSStrings etc..
I think I'm missing some easy way out.
Show it to me please.
You need to capture an object in the block that you can send the response object.
This can be self.
-(void)processUserDetails:(InstagramUser *) userDetail
{
//....
}
- (void)getSelfUserDetails
{
[[InstagramEngine sharedEngine] getSelfUserDetailsWithSuccess:^(InstagramUser *userDetail) {
[self processUserDetails: userDetail];
} failure:^(NSError *error) {
}];
}
You could create a property to hold the Instagram user that you find and assign it to it in the success block:
#property (nonatomic) InstagramUser *myUser;
- (void)getSelfUserDetails
{
[[InstagramEngine sharedEngine] getSelfUserDetailsWithSuccess:^(InstagramUser *userDetail) {
NSLog(#"%#",userDetail);
self.myUser = userDetail;
} failure:^(NSError *error) {
}];
}
This is a good use for an NSNotification (since the call above happens asynchronously).
You could call it like:
[[NSNotificationCenter defaultCenter]
postNotificationName:#"TestNotification"
object:self
userInfo:#{ #"userDetail" : userDetail }
];
And then get that userInfo data back with whatever method is listening for that event.
I've working on/learning this all afternoon.
Following an example here: http://themainthread.com/blog/2012/09/communicating-with-blocks-in-objective-c.html, I have managed to setup a callback to get the result of an asynchronous call to a web service i have.
The web service takes a key code and the app transforms it and passes it back for authentication.
With my code below, how can I change the method from a void to an NSString that I can call to return my pass code?
-(void) showPassCode{
getAuthCodeAndMakePassCodeCompleteBlock callback = ^(BOOL wasSuccessful, NSString *passCode) {
if (wasSuccessful) {
NSLog(#"Code is: %#", passCode);
} else {
NSLog(#"Unable to fetch code. Try again.");
}
};
[self getAuthCodeAndMakePassCode:#"myAuthCode" withCallback:callback];
}
Ideally, I want it to work or look like this:
-(NSString *) strPassCode{
getAuthCodeAndMakePassCodeCompleteBlock callback = ^(BOOL wasSuccessful, NSString *passCode) {
if (wasSuccessful) {
return passCode;
} else {
return nil;
}
};
[self getAuthCodeAndMakePassCode:#"myAuthCode" withCallback:callback];
}
Without knowing the specifics of your code and how you query the server, I have to imagine it would look something like:
-(void)getAuthCodeWithCallback:(void (^)(NSString* authCode))callback
{
//make server call, synchronously in this example
NSString* codeReturnedFromServer = [self getServerCodeSynchronous];
callback(codeReturnedFromServer);
}
//some calling code
[self getAuthCodeWithCallback:^(NSString* authCode) {
NSLog(#"Code is: %#", authCode);
}];
If the method that gets your auth code from the server is asynchronous, it would look something like this:
-(void)getAuthCodeWithCallback:(void (^)(NSString* authCode))callback
{
//make server call, asynchronously in this example
[self someMethodCallToQueryCodeFromServerWithCallback:^(NSError* error, NSString* code) {
if (error) {
//handle error
}
else
callback(code);
}
}
I have been trying to use dispatch_async in a method that returns a result. However, I observed that the method returns before executing the dispatch_async block. Due to this I'm not getting the results I expect. Here is some code that demonstrates my problem.
-(BOOL) isContactExists {
BOOL isContactExistsInXYZ = YES;
UserId *userId = contact.userId;
dispatch_async(dispatch_get_main_queue(), ^
{
iOSContact *contact = [iOSContact contactForUserId:userId];
if (nil == contact)
{
isContactExistsInXYZ = NO;
}
});
return isContactExistsInXYZ;
}
This method isContactExists is called somewhere else and based on the response from that method I have to do some stuff. But every time, the value of isContactExistsInXYZ is not what I expect. How do I handle dispatch_async in this situation?
If your going the block route your method needs to look something like this.
- (void)isContactExistsWithCompletionHandler:(void(^)(BOOL exists)) completion
{
dispatch_async(dispatch_get_main_queue(), ^
{
BOOL isContactExistsInXYZ = YES;
UserId *userId = contact.userId;
iOSContact *contact = [iOSContact contactForUserId:userId];
if (nil == contact)
{
isContactExistsInXYZ = NO;
}
completion(isContactExistsInXYZ);
});
}
And where you are calling it something like this.
[someObject isContactExistsWithCompletionHandler:^(BOOL exists) {
// do something with your BOOL
}];
You should also consider placing your heavy operations in a other que than main. Like this.
- (void)isContactExistsWithCompletionHandler:(void(^)(BOOL exists)) completion
{
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, NULL);
dispatch_async(queue, ^
{
BOOL isContactExistsInXYZ = YES;
UserId *userId = contact.userId;
iOSContact *contact = [iOSContact contactForUserId:userId];
if (nil == contact)
{
isContactExistsInXYZ = NO;
}
dispatch_async(dispatch_get_main_queue(), ^
{
completion(isContactExistsInXYZ);
});
});
}
You need to respect that what you are trying to do is asynchronous and embrace that. This means not using a return value. Instead you can write your method to take a callback block as a parameter. Then, when your asynchronous check is complete you can call the block with the result.
So your method signature would become:
- (void)checkIfContactExistsWithCompletion:(ContactExistsBlock)completion {
Where ContactExistsBlock is a block definition with no return and probably a single BOOL parameter.
typedef void (^ContactExistsBlock) (BOOL exists);
The reason is dispatch_async(dispatch_get_main_queue(), ^does not wait until execution is done. You are probably messing up stuff there. Normally, this is used to update UI asynchronously along with other server content getting downloaded in some other thread. Try using dispatch_sync instead.