activerecord - Querying through several models in Rails 3 -

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i have several models:

workspace user asset workspaceuser workspaceasset

workspace has many users , assets, through 2 join tables (workspaceuser, workspaceasset)

i'm trying find efficient , elegant way find out if there exists path between user , asset, ie user -> workspaceuser -> workspace -> workspaceasset -> asset

this have far:

workspace.joins(:workspace_assets, :workspace_users).where("workspace_assets.asset_id = ? & workspace_users.user_id = ?", assetid, userid)

was hoping better solution , perhaps 1 return asset in question.

have tried:

asset.joins(:workspace_assets => {:workspace => :workspace_users}.  where("assets.id = ? & workspace_users.user_id = ?", assetid, userid)

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