ios - Using NSURLSession to download a lot of images -


i have created simple testing app learn how use nsurlsession. app has download images webservice , present them uitableview. i've written first part of app reads list of images urls web service, now, want display list.

my doubt is:

given list of images long list, ok create nsurlsessiondownloadtask each image? thought create session in cellforrowatindexpath function , store nsurlsessions in nsdictionary using key indexpath of cell (and relying on nsurlcache avoid download same images more once).

other solutions:

i can see 3 more solutions:

  1. using gcd dispatch_async

  2. subclassing nsoperation , store nsoperation image need download.

  3. using third party library afnetwork... since learning purpose app prefer go code .

if multiple nsurlsession isn't solution, i'd choose 1 of options.

what think approach?

nsurlsessiontask fine large number of downloads. 1 advantage of on of other methods mentioned downloads can cancelled or paused. correctly implements concurrency network operations, more difficult many cats on internet lead believe (if don't believe me, view eskimo's 2010 wwdc session , sample code. nsoperation network connections not trivial).

nsurlsessiontask , friends designed kinds of problems trying solve, , it's tested.

for tableview, start task in tableview:willdisplaycell:forrowatindexpath: , cancel (or pause) task in tableview:didenddisplayingcell:forrowatindexpath:. limit active downloads visible cells.


Comments

Post a Comment

Popular posts from this blog

javascript - RequestAnimationFrame not working when exiting fullscreen switching space on Safari -

request animation frame stops working when exiting fullscreen clicking on original space's safari window. fine if fullscreen mode canceled escape key or calling cancelfullscreen(). steps reproduce: open https://dl.dropboxusercontent.com/u/769042/prezi/safari-fullscreen.html click "draw raf", kittie appears click "fullscreen", go fullscreen click "draw raf", kittie appears go space original safari was, showing "click exit fullscreen mode", click anywhere, out fullscreen click "draw raf", nothing happens what handling click calling: window.requestanimationframe(draw); which draws on canvas context: function draw() { ctx.drawimage(img, math.random()*500|0, math.random()*400|0, 100, 100); } i checked .hidden , .visibilitystate, updated correctly. tested on osx 10.9.3, safari 7.0.4 (9537.76.4). has workaround/solution other switching old settimeout? this sounds webkit bug 88940 : using reque...
Read more

Why am I getting Internal .NET Framework Data Provider error 1025 when passing Method to where? -

i have method takes generic tentity overriden. it's signature follows: public virtual expression<func<aclproject, bool>> projectfilter(params tentity[] objs) { return (p) => objs.select(o => o.id).contains(p.id); } i filter query based on this: from p in db.somedbset db.aclprojects.where(projectfilter(p)).any() select p this results in 1025 error. (note doesn't matter body of projectfilter is, error still occurs. any ideas why? thanks!
Read more

postgresql - how to get points from linestring postgis -

i have linestring (0 0 , 2 4 , 5 5); i need output in form : x (1st cell) || y (2nd cell) 0 || 0 2 || 4 5 || 5 and same polygon. how ? you can use st_x , st_y in conjunction st_pointn x , y of individual points, , use generate_series create index each point of linestring, eg, with line (select st_geomfromtext('linestring(0 0, 2 4, 5 5)') geom) select st_x(st_pointn(geom,num)) x, st_y(st_pointn(geom,num)) y line, (select generate_series(1, (select st_numpoints(geom) line)) num) series;
Read more