php - saving hasMany always add record instead of updating -

i have hasmany relationship (let's post hasmany comments)

i want edit both post , existing comment @ same time

my code

in comment edit.ctp file did

<?= $this->form->create($post); ?> <?= $this->form->input('title'); ?>  <?= $this->form->input('title');  ?> <?= $this->form->input('text'); ?> <?= $this->form->input('comments.0.id'); ?> <?= $this->form->input('comments.0.text'); ?> 

and in postscontroller

$post= $this->posts->get($id); $post= $this->posts->patchentity($post, $this->request->data, ['associated' => ['comments']]); 

my problem

now expect comment updated, instead cake adds new comment every time.

what did do

i tried debug $this->request->data , got

[     'text' => 'this test',     'comments' => [         (int) 0 => [             'id' => '168',             'text' => 'comment test',          ]     ] ] 

but if debug $post get

object(app\model\entity\post) {      /* ... */     'comments' => [         (int) 0 => object(app\model\entity\comment) {              'text' => 'comment test',             '[new]' => true,             '[accessible]' => [                 '*' => true             ],             '[dirty]' => [                 'text' => true             ],             /* ... */          }     ],     /* ... */     '[dirty]' => [         'comments' => true,     ],  }    

so why comment marked 'new' when pass id controller?

of course on simplified version of actual situation. maybe problem it's not in above code , have elsewhere in other code.

my question here if i'm doing basic approach error.

you need read associated data entity in order able patch it, otherwise data won't merged, marshalled, , ends being handled "new".

automatically loading associated data happens special _ids key, , when there @ least 1 entry in association property, ie don't need have associated data loaded want patch, there must something in order marshaller reach point data being read , merged.

to exact, without data in comments property, marshaller step out here

https://github.com/cakephp/cakephp/blob/3.2.8/src/orm/marshaller.php#l653-l655

i can't tell whether there might bug, @ least guess docs need updated around this, little misleading. while try explain happens when associated data missing in source entity, shown example doesn't work, , new entities created belongsto , hasone associations, incorrect.

cookbook > database access & orm > saving data > patching hasmany , belongstomany

you may want file issue on @ github clarification.

tl;dr

long story short, contain comments , should good.

$post = $this->posts->get($id, [     'contain' => ['comments'] ]); // ...