1. Change a integer into string (actually it is a array of char) 2. Revese the string 3. Change the string into the number
reverseNumber :: Int -> Int reverseNumber n = read (reverse (show n)) :: Int reverseNumbers l = map (reverseNumber) l
In the previous tutorial about a half year ago, I talked about how to create a simple delayed email with the great gem, delayed job. In the tutorial, the delayed duration is a constant for every object. But if you want to do this based on different condition, say the attribute of the delayed object. You can simply create a new Job Class and enquene the job with delay.
class NewJob
def initialize(job)
@job = job
end
def perform
Notifier.job_created(@job).deliver
end
end
In the controller, you can enqueue the job to run at a specific time. I have used random number to simulate the random situation of the delayed time of each job.
delayed_time = Random.rand(1..10).minutes.from_now Delayed::Job.enqueue(NewJob.new(@job) , :run_at => delayed_time)
many libraries are like that!!!, you have to declare both instance variable, @property for getter and setter
// header file:
@interface Person :NSObject{
NSString *name;
}
@property (strong, nonatomic) NSString *name;
@end
// implementation file
@implementation
// create getter and setter
@synthesize name;
@end
Many books or tutorials use it You don't have to decleare the instance variable, but you still have to @syntheize to get getter & setter
// header file:
@interface Person :NSObject
@property (strong, nonatomic) NSString *name;
@end
// implementation file
@implementation
// create getter and setter
@synthesize name;
@end
supported by LLVM 4.0 or above Auto synthesize all getter & setter and to delcare instance varable All instance variables are with prefix _. You can access _name in the implementation file, while the other class access that variable by [object.name]
// header file:
@interface Person :NSObject
@property (strong, nonatomic) NSString *name;
@end
// implementation file
@implementation
//.. auto @synthesize
@end
The syntheize instance variables just belongs to that class, if you want to inherit from that class, and to access the property as instance variabel in the sub class, you need to do the @syntheize in the sub class
// header file of super class:
@interface Person :NSObject
@property (strong, nonatomic) NSString *name;
@end
// header file of sub class
#import "person.h"
@interface Teacher : Person
@end
// implementation file of sub class
@implementation
@synthesize name = _name // access public class's property as instance variable
@end
I have made command line Base64Converter which uses Ruby Standard Library to convert a image into Base64Encoded String.
Instead, I want it to have Standard output, I may improve it later :)
Download here
In the previous tutorial, you will be able to create a Simple iOS application
and a simple rails application.
In this last tutorial, you will know how to send the image from iphone simulator to rails web application.
There are two common way to send image, one is to use the form data request, one is to use Base64 to encode the image data byte into ASCII code so that the encoded image data can be sent with JSON request.
Assume you have put the library into the XCode project,
then import NSData+Base64.h into BIDViewController.m in order to get the ability to encode the image data.
- (IBAction)sendImage:(id)sender {
// Encode the Image with Base64
NSData *imageData = UIImagePNGRepresentation(_imageView.image);
NSString *imageDataEncodedeString = [imageData base64EncodedString];
// Send Request to Server
// Create the request with url
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:@"http://localhost:3000/accounts.json"]];
// Add header value and set http for POST requeest as JSON
[request addValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
[request setHTTPMethod:@"POST"];
NSLog(@"Htttp Method%@ ", request.HTTPMethod);
// Create dictionary key-value pair for transformming into NSData
NSMutableDictionary *newAccount = [[NSMutableDictionary alloc]init];
[newAccount setObject:_nameTextField.text forKey:@"name"];
[newAccount setObject:imageDataEncodedeString forKey:@"icon_image_data"];
NSLog(@"%@", newAccount);
//transform the dictionary key-value pair into NSData object
NSData *newAccountJSONData = [NSJSONSerialization dataWithJSONObject:newAccount options:NSJSONReadingMutableContainers error:nil];
//let the NSData object be the data of the request
[request setHTTPBody:newAccountJSONData];
//create connection with the request and the connection will be sented immediately
NSURLConnection *connection = [[NSURLConnection alloc]initWithRequest:request delegate:self];
// the connection created is successfully
if (connection) {
_receivedData = [[NSMutableData alloc] init];
}
}
The prevous step only made the connection to the URL, the controller have to owns a NSMutableData in order to holds the data received from the connection.
@interface BIDViewController ()
@property (strong, nonatomic) NSMutableData *receivedData;
@end
// delege meethod of NSURLConnection
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{
[_receivedData appendData:data];
}
-(void)connectionDidFinishLoading:(NSURLConnection *)connection{
// parsing the return JSON Sting
/* {"created_at":"2012-12-15T22:33:59Z","icon_url":"/icon/3.png","id":3,"name":"jason","updated_at":"2012-12-15T22:33:59Z"} */
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Connection" message:@"Connection Finished" delegate:self cancelButtonTitle:@"I know!" otherButtonTitles:nil];
[alert show];
}
-(void) connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
if ([response isKindOfClass:[NSHTTPURLResponse class]])
{
NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse*) response;
NSLog(@"%d", [httpResponse statusCode]);
//If you need the response, you can use it here
}
}
Add this method into model- account.rb It will decode the image data into IOObject.
def decode_icon_image_data
# if the icon_image_data is set
# decode it and handle by controller method
if self.icon_image_data.present?
data = StringIO.new(Base64.decode64(self.icon_image_data))
data.class.class_eval {attr_accessor :original_filename, :content_type}
data.original_filename = self.id.to_s+".png"
data.content_type = "image/png"
return data
end
end
In the controller we set up in the previous tutorial, we will check either the data from remote or from local. icon_io = @account.icon_image || @account.decode_icon_image_data So we don't have to change the controller.
This result is expected, you will see a long JSON request parameter in terminal.
I have made a shell script for testing the server side, it hard code the JSON data used to register a member called jason with blue flower icon. You can download it from
Use it as sh curl_test.sh
Happy new year :)
Test attr_accessor though two simple programs
No instance variable declartion
class Car
attr_accessor :band, :price
end
car = Car.new
puts "Band nil ? #{car.band.nil?}" # => Band nil? true
puts "Price nil? #{car.price.nil?}" # => Price nil? true
Explicitly declare instance variable in method initalize
class Car
attr_accessor :band, :price
def initialize(args)
@band = args[:option]
@price = args[:price]
end
end
car = Car.new(:option=>"Bentz", :price=>100000)
puts "Band nil ? #{car.band.nil?}" # => Band nil? true
puts "Price nil? #{car.price.nil?}" # => Price nil? true
attr_accessor just created setter&getter method
it doesn't declare the instance variable for you,
Util you declare the instance variable explicitly.
In Example 1, if you tried to print out the two variable like car.band
& car.price, you will actually get nothing returned