Chapter 5. A Model Expressed In Software Flashcards
An association in the model means there is what in the software?
A mechanism with the same properties.
DDD, p. 82
Three ways to make associations more tractable are:
Impose a ________ direction
Add a _________ (effectively reducing multiplicity)
Eliminate _________ associations
- traversal direction. (e.g a country has a president)
- Add a qualifier, (e.g,, a country has only one president during a particular period)
- nonessential associations
DDD, p. 83
An object defined primarily by its identity is called an __________.
Entity
DDD, p. 91
For an entity, an identifying attribute must be guaranteed to be _______ within the system.
Unique
DDD, p. 92
For an entity, an identifying attribute must be guaranteed to be _______ within the system.
Unique
DDD, p. 92
Value objects are instantiated to represent elements that we care about only for ________ they are, not _________ or _______ they are.
What
Not who or which
DDD, p. 98
When creating property for value object in Obj-C , the defaulting qualifier is which: atomic or nonatomic?
Nonatomic
ObjC.io issue on Foundation, Value Objects
By default properties are Strong or Copy?
Strong
ObjC.io issue on Foundation, Value Objects
Where else could the ‘copy’ qualifier be assigned?
in the implementation.
_name = [ name copy ];
ObjC.io issue on Foundation, Value Objects
For an immutable object, when do you want to assign Copy to a property?
When there is a mutable counterpart to the type. E.g. string
@property (nonatomic,copy) NSString* name;
ObjC.io issue on Foundation, Value Objects
How can you compare to value objects?
implement the isEqual method using all properties and implement a hash function
ObjC.io issue on Foundation, Value Objects
What is a hash?
a pseudorandom number generated from the object’s properties.
ObjC.io issue on Foundation, Value Objects
What are two good qualities of a hash?
deterministic and uniform
ObjC.io issue on Foundation, Value Objects
If the properties that go into a hash value change, what else changes?
the hash value… bad… make sure things are immutable
From objc article on value objects
The code should contain an _________ that is guaranteed to produce a ________ result for each entity object.
operation
unique
DDD, p.92
How are properties a convenience for objective-c programmers?
when synthesizes, properties give you automatic getters and setters.
inferred from iOS programming (Big Nerd), p. 72
How many property attributes are there?
Three
iOS programming (Big Nerd), p. 72
Most objective-c programmers use which of these: atomic or nonatomic?
Nonatomic
iOS programming (Big Nerd), p. 73
When would you use atomic as a property value?
for multi-threaded applications.
iOS programming (Big Nerd), p. 73
Which is the default property? Atomic or nonatomic.
Atomic. Will always need to explicitly declare nonatomic.
iOS programming (Big Nerd), p. 73
Multi-threaded or concurrent programming allows you to take advantage of multiple _______.
CPUs
ObjC.io issue on Concurrent Programming, Editorial
Which is the default property qualifier: readwrite or readonly?
readwrite
iOS programming (Big Nerd), p. 73
Which property qualifier would you want to use for a value object? : readwrite or readonly
Readonly. This makes them immutable which is a required characteristic of value objects.
ObjC.io issue on Foundation, Value Objects
Which of these property qualifiers is default: strong or assign?
It depends on the type of property!
iOS programming (Big Nerd), p. 73
A property whose type is not a pointer to an object (scalar property), like -int-, does not need memory management and thus defaults to which one: strong or assign?
assign
iOS programming (Big Nerd), p. 73
For pointers to objects which is the default: strong or assign?
strong
iOS programming (Big Nerd), p. 73
When you have a property that points to an instance of a class that has a mutable subclass (like NSString or NSArray) which should be the qualifier: strong or copy?
Copy
iOS programming (Big Nerd), p. 76
When pointing at a mutable subclass and not using copy, the item can be ________ without knowledge of the object that also points to it.
changed.
iOS programming (Big Nerd), p. 77
Bidirectional associations do or do not make sense between value objects?
do not make sense because you could not say that one value objects points directly to the one pointing to it - no identity.
DDD, p. 102
When we force an operation into an object that doesn’t fit the objects’s definition, the object loses its ___________ and becomes hard to understand or ___________.
conceptual clarity
refactor
DDD, p. 104
One should use a service when _________ is actually an important domain concept.
an operation
DDD, p. 105.
In object oriented programming, an interface generally defines the set of ________ that an instance of a class that has that_______ could _______ to.
the set of methods (or messages)
interface
respond.
http://stackoverflow.com/questions/2866987/what-is-the-definition-of-interface-in-object-oriented-programming
When you write an interface, you’re basically saying:
“I need something that…”
http://stackoverflow.com/questions/2866987/what-is-the-definition-of-interface-in-object-oriented-programming
A good service relates to a __________ that is not a natural part of an _______ or _________.
domain concept
entity
value object
DDD, p. 105
A good service is an _________ that is defined in terms of the __________ in the domain model.
interface
other elements
DDD, p, 105
T/F A good service is stateless.
True
DDD, p, 105
For a service, statelessness means that any ________ can use any instance of a particular service without regard to the instance’s ______________.
client
individual history
(If a class Cheetos Bag implements the Chip Bag interface, you should expect a Cheetos Bag to behave exactly like any other Chip Bag. (That is, expose the .attemptToOpenWithoutSpillingEverywhere() method, etc.)
DDD, p. 105
An interface indicates ________ of the object that implements the interface.
capability
(Walkable might be a good interface to have if your system has many things that can walk.)
http://stackoverflow.com/questions/444245/how-will-i-know-when-to-create-an-interface
T/F A service should be implemented as a phony object.
False, this would be misleading.
DDD, p. 105
Services can appear in which layers?
Application, domain, or infrastructure
DDD, p. 106
If the operation for a service has any meaning in the domain then it should be in the ______.
Domain model
DDD, p.106
What is meant by “clients” in the OOP world?
In the gof book, the client is the code or class that is using the classes in the pattern.
http://stackoverflow.com/questions/15847806/client-concept-in-oop-design-patterns
A distributed system is a ________ of independent computers that appears to its users as a _________ system (Tanenbaum, van Steen)
collection
single, coherent
http://www.win.tue.nl/~johanl/educ/2II45/ADS.02.Distributed.pdf
The primary motivation for using modules is ___________.
cognitive overload
DDD, p.109
There should be _______ cohesion between modules and _____ cohesion within them.
low
high
DDD, p,109
True / False: Modules (packages) can be implemented in Objective-C.
False.
http://stackoverflow.com/questions/1000707/objective-c-equivalent-of-java-packages
Refactoring modules are more or less work than refactoring classes?
More
DDD, p.110
If your model is telling a story, the modules are _______.
chapters
DDD, p.110
With packages, Java can have two _______ with the same name “connection”
Classes
e. g.,
com. cod3r.app.network.Connection and com.cod3r.app.database.Connection
In Java, the_____ name gets longer where as in Objective-C the ______ name gets longer.
package
class
http://www.cod3r.com/2011/01/what-objective-c-can-learn-from-java-part-4-namespace/
for a helpful overview of packages in Java see:
http://docs.oracle.com/javase/tutorial/java/package/index.html
The difference is [in Java] the fully qualified ________ would only be used in the _____ statement, and the short _______ would be used in the code, instead of the _______ used in every location as seen in Objective-C.
class name short class name really long classname
http://www.cod3r.com/2011/01/what-objective-c-can-learn-from-java-part-4-namespace/
Most systems must use some non object technical infrastructure, most commonly ___________.
relational databases
DDD, p. 120
The most effective tool for holding the parts [from mixed paradigms] together is a robust _________ that underlies the whole heterogeneous model.
ubiquitous language
DDD, p. 121
Before taking on the burden of mixed paradigms, the options within the _________ should be exhausted.
dominant paradigm
DDD, p. 122
