get images from URL into an array in objective-c

Question

I am wanting to get an array of all the urls to images from a page.

Javascript:

<script>
function newEl(tag){return document.createElement(tag);}

window.addEventListener('load', onDocLoaded, false);

function onDocLoaded()
{
    myAjaxRequest("http://foo.com/bar.html", onHtmlLoaded);
}

function onHtmlLoaded(ajax)
{
    var div = newEl('div');
    div.innerHTML = ajax.responseText;
    var imgs = div.getElementsByTagName('img');


    for (var i=7;i<imgs.length;i++)
    { 
    document.write("<p id='"+i+"'>"+imgs[i].src+"<p/>");
    }
}

function myAjaxRequest(url, callback)
{
    var ajax = new XMLHttpRequest();
    ajax.onreadystatechange = function()
    {
        if (this.readyState==4 && this.status==200)
            callback(this);
    }
    ajax.onerror = function()
    {
        console.log("AJAX request failed to: " + url);
    }
    ajax.open("GET", url, true);
    ajax.send();
}
</script>

What I have done here, is to get a page (www.foo.com/urls.html) full of all the image urls from http://foo.com/bar.html through javascript which looks like this:

HTML:

<p id="1">http://www.foo.com/x.jpg</p>
<p id="2">http://www.foo.com/y.jpg</p>
<p id="3">http://www.foo.com/z.jpg</p>
...

I want to then be able to create an array of all the urls in objective c would that be possible?

is there a better way to do it than this?

meda · Accepted Answer · 2014-05-07 13:51:08Z

You should store the images url into your database.

Write a script to get those images and put then into a json array

PHP

<?php
$mysqli = new mysqli("example.com", "user", "password", "database");
if ($mysqli->connect_errno) {
    echo "Failed to connect to MySQL: (" . $mysqli->connect_errno . ") ";
}

$res = $mysqli->query("SELECT image_name FROM images");


$data=array();
while ($row = $res->fetch_assoc()) {
    $data['images'][] = $row['image_name']; 
}

echo json_encode($data);
?>

Then from your iOS app make a request the JSON data PHP script.

JSON:

{
    "images": [
        "http: //xxxxxxxxx.co.uk/video%20images/ONYX%20sofa.jpg",
        "http: //xxxxxxxxx.co.uk/video%20images/aaron%20duran.jpg",
        "http: //xxxxxxxxx.co.uk/video%20images/littledragon.jpg",
        "http: //xxxxxxxxx.co.uk/video%20images/cantalivering%20house.jpg"
    ]
}

Finally in your app store it into an array.

IOS

NSURL *url = [NSURL URLWithString:@"http://www.url.com/get_images.php"];
//Creating the data object that will hold the content of the URL
NSData *jsonData = [NSData dataWithContentsOfURL:url];
NSError *error = nil;
//parse the JSON
NSDictionary *result = [NSJSONSerialization JSONObjectWithData:jsonData 
                              options:NSJSONReadingMutableContainers error:&error];
//Here is the array
NSArray *images = result[@"images"];
NSLog("images =%@", images);

kerryknight · Accepted Answer · 2014-05-06 14:36:05Z

0

While I'm not 100% certain I understand your issue and what you're trying to accomplish, it sounds to me like you're trying to:

Run your JS code and have your URLs print out in an HTML page
At the same time you're generating your HTML page's list of URLs, you want to collect those same URLs in an array for use within and iOS project.

This can be done with the new JavaScriptCore framework in iOS. I must say that the inspiration for this answer I owe whole-heartedly to the excellent chapter on JavaScriptCore by Pietro Rea in iOS 7 by Tutorials from RayWenderlich.com. It's an absolute must read for this type of stuff.

To arrive at your solution (for our purposes, I'll assume your array is being manipulated within an iOS view controller), you'll need to refactor your JavaScript file's code a bit so that you can build your Objective-C array at the same time you build your HTML page. Also, instead of creating the HTML page when your js/html files have loaded, I would allow my iOS view controller to control when this occurs.

MyJavascriptFile.js: (Ensure you include this file in the Copy Bundle Resources section of your iOS Project

<script>
function newEl(tag){return document.createElement(tag);}

//replace previous on load function call with function 
//that is called from Objective-C
function onObjectiveCLoaded() {
    myAjaxRequest("http://foo.com/bar.html", onHtmlLoaded);
}

function onHtmlLoaded(ajax) {
    var div = newEl('div');
    div.innerHTML = ajax.responseText;
    var imgs = div.getElementsByTagName('img');


    for (var i=7;i<imgs.length;i++) { 
        document.write("<p id='"+i+"'>"+imgs[i].src+"<p/>");

        //also, add our url to our objective-c array at same time            
        //this function is defined in MyViewController.m iOS file
        addURLToObjectiveCArray(imgs[i].src);
    }
}

function myAjaxRequest(url, callback) {
    var ajax = new XMLHttpRequest();
    ajax.onreadystatechange = function() {
        if (this.readyState==4 && this.status==200)
            callback(this);
    }
    ajax.onerror = function() {
        console.log("AJAX request failed to: " + url);
    }
    ajax.open("GET", url, true);
    ajax.send();
}
</script>

Now, in our iOS Project:

Header file:

//  MyViewController.h

#import <UIKit/UIKit.h>
#import <JavaScriptCore/JavaScriptCore.h>

@interface MyViewController : UIViewController
//this is required execution environment to run JS code locally
@property (strong, nonatomic) JSContext *jsContext;
@end

Implementation file:

//  MyViewController.m

#import "MyViewController.h"

@interface MyViewController ()
@property (strong, nonatomic) NSMutableArray *myArrayOfURLs;
@end

@implementation MyViewController
- (void)viewDidLoad {
    [super viewDidLoad];

    //init our array
    self.myArrayOfURLs = [NSMutableArray new];

    //get a path to the javascript file we included in our bundle
    NSString *javascriptPath = [[NSBundle mainBundle] pathForResource:@"MyJavascriptFileName" ofType:@"js"];

    //turn our entire JS file into single string which we'll execute in our JS context
    NSError *error = nil;
    NSString *javascriptString = [NSString stringWithContentsOfFile:javascriptPath encoding:NSUTF8StringEncoding error:&error];

    if (error) {
        NSLog(@"Oops. Something happened.");
        return;
    }

    //init our context and evaluate our string of javascript
    self.jsContext = [[JSContext alloc] init];
    [self.jsContext evaluateScript:javascriptString];

    //grab a weak reference to self so we don't create strong retain cycle
    //within the block callback we're about to create
    __weak MyViewController *wSelf = self;

    //define the method/function we're calling from our JS file to add url to array
    //as we're creating our HTML page in our JS file, our JS file will call this
    //addURLToObjectiveCArray callback, passing in the current URL so we can add it
    self.jsContext[@"addURLToObjectiveCArray"] = ^(NSString *url) {
        [wSelf.myArrayOfURLs addObject:url];
    };

    //to ensure we don't prematurely create our url list in the JS file only,
    //only call that part of your JS file code from a function call here via
    //our context
    JSValue *jsFunction = self.jsContext[@"onObjectiveCLoaded"];
    [jsFunction callWithArguments:@[]];
}
@end

Don't forget to import the JavaScriptCore framework into your iOS project! While I'm unable to test this solution at present, it should certainly be enough to get you started. Again, I can't stress enough how awesome the raywenderlich.com tutorial is on this subject so check it out for the full explanation of everything here.

answered May 6, 2014 at 14:36

kerryknight

416 bronze badges

4 Comments

maxisme Over a year ago

Thank you very much! I am just receiving this error

maxisme Over a year ago

2014-05-07 13:46:12.457 Bits & Bobs[5667:60b] Oops. Something happened. 2014-05-07 13:46:12.463 Bits & Bobs[5667:60b] Unable to simultaneously satisfy constraints. Probably at least one of the constraints in the following list is one you don't want. Try this: (1) look at each constraint and try to figure out which you don't expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints) (

maxisme Over a year ago

"<NSLayoutConstraint:0x17009bf30 V:[UIScrollView:0x12750b720]-(0)-| (Names: '|':UIView:0x170161440 )>", "<NSLayoutConstraint:0x17009bfd0 V:[UIScrollView:0x12750b720]-(-1)-| (Names: '|':UIView:0x170161440 )>" ) Will attempt to recover by breaking constraint <NSLayoutConstraint:0x17009bf30 V:[UIScrollView:0x12750b720]-(0)-| (Names: '|':UIView:0x170161440 )> Break on objc_exception_throw to catch this in the debugger. The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.

kerryknight Over a year ago

Unfortunately, that issue is related to your auto layout constraints not being properly set up--a completely different issue from your original one. This new problem is independent of what you're doing when sending JavaScript objects to an iOS environment. As layout issues can be a little tough to diagnose from code, I might suggest another awesome raywenderlich.com tutorial on beginning auto layout. As for collecting the URLs from JavaScript in an NSArray, did the solution posted above work for you?

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