Components: md-select: add compareWith function

[kara]

Currently, md-select values are compared by object reference. This is a bit inflexible. We want to allow people to compare options by a custom comparator in case they only care about the object's ID or some other property.

Example markup:

<md-select placeholder="Food" [(ngModel)]="food" [compareWith]="compareById">
   <md-option *ngFor="let food of foods" [value]="food"> {{ food.name }} </md-option>
</md-select>

compareById(obj1, obj2) {
   return obj1.id === obj2.id;
}

This will be parallel to functionality being added to native selects in core.

[jt-helsinki]

@kara is this still being considered?

[mackva]

What news?

[linuradu]

Sounds good, regarding commit :) When will be the next release?

[pdavin-zz]

Any update on this? Looks like there's a fix in a forked branch but not submitted for PR / review yet.

[kweinmeister]

It looks like there is a PR, but it now has a merge conflict: https://github.com/angular/material2/pull/4540

[jeanpchr]

Has anyone implemented a workaround for this issue?

[ppham27]

I have PR #4540 open. I'm pretty good about rebasing it pretty often, so if you really need the feature, you could build against my branch. I'm not sure when/if they plan on merging it into master.

[reppners]

Desperately need this 👍

[picheli20]

For me only solved when I've change the ngModel to value. Like:

<md-select placeholder="Food" [(value)]="food" [compareWith]="compareById">
   <md-option *ngFor="let food of foods" [value]="food"> {{ food.name }} </md-option>
</md-select>

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