NSOperation dependency creep

Example.m

NSMutableDictionary *context = [NSMutableDictionary dictionary];

// Adds information in context under the key "fromOp1"
Op1 *op1 = [[Op1 alloc] initWithContext:context];

// Consumes "fromOp1" from context and add info under the key "fromOp2"
Op2 *op2 = [[Op2 alloc] initWithContext:context];
[op2 addDependency:op1];

// Adds info in context under the key "fromOp3"
Op3 *op3 = [[Op3 alloc] initWithContext:context];

// Consumes "fromOp3" from context and add info under the key "fromOp4"
Op4 *op4 = [[Op4 alloc] initWithContext:context];
[op4 addDependency:op3];

// Add info under the key "fromOp5"
Op5 *op5 = [[Op5 alloc] initWithContext:context];
[op5 addDependencies:@[op2, op4]];

// Consumes "fromOp2", "fromOp4" and "fromOp5" from context.
Op6 *op6 = [[Op6 alloc] initWithContext:context];
[op6 addDependency:op5];

The reason "context" is being sent to all the operations is that the results are needed in each step of the dependency chain.