Now speed piece the half squares, by stacking a Color 3 and Color 1 3-7/8" x 31"strip, right sides together. On the back of the top strip lightly mark the 3-7/8" square lines. Mark the diagonals in the direction shown at left as well. Sew a SCANT 1/4" above and below the marked diagonals, pivoting at the 3-7/8" square lines. Cut apart ON the marked diagonals, and on the square lines. This will give you sixteen half squares. Press seam allowances towards the darker fabric. Repeat this with a Color 3/Color 2 set, and again with a Color 1/Color 2 set... ...on to Page 2! To do this as a 12" finished block, the squares need to be cut at 2"( you need four of Color 2 and twelve of Color 3) ...the half squares are pieced as above from 2-3/8" x 19" strips. Trim half squares to measure 2" if needed, after pressing to dark side. March2000 Marcia Hohn Traditional Block
Typically, the observer pattern is implemented with the "subject" (which is being "observed") being part of the object whose state change is being observed, to be communicated to the observers upon occurrence. This type of implementation is considered " tightly coupled ", forcing both the observers and the subject to be aware of each other and have access to their internal parts, creating possible issues of scalability , speed, message recovery and maintenance (also called event or notification loss), the lack of flexibility in conditional dispersion and possible hindrance to desired security measures. In some ( non-polling ) implementations of the publish-subscribe pattern (also called the pub-sub pattern), this is solved by creating a dedicated "message queue" server and at times an extra "message handler" object, as added stages between the observer and the observed object whose state is being checked, thus "decoupling" the software components. In these cases, the message queue server is accessed by the observers with the observer pattern, "subscribing to certain messages" knowing only about the expected message (or not, in some cases), but knowing nothing about the message sender itself, and the sender may know nothing about the receivers. Other implementations of the publish-subscribe pattern, which achieve a similar effect of notification and communication to interested parties, do not use the observer pattern altogether.