Changes for page WebObjects and Squeryl

Summary

• Page properties (3 modified, 0 added, 0 removed)

Details

Page properties

Parent

...	...	@@ -1,0 +1,1 @@
	1	+WebObjects with Scala

Tags

...	...	@@ -1,0 +1,1 @@
	1	+webobjects|scala|squeryl|eof

Content

...	...	@@ -1,23 +1,77 @@
1		-= Squeryl ~= //SQL-like// DSL for Scala =
	1	+= Squeryl ~= //SQL-like// DSL in Scala =
2	2
3		-Advantages of Squeryl over EOF:
	3	+Advantages of [[Squeryl>>url:http://squeryl.org/||shape="rect"]] over EOF:
4	4
5	5	* Concurrent
6	6	** Spawns multiple database connections
7	7	** Issues database transactions concurrently
8	8	* Scala Actor compatible
9		-* Immutable object model/graph
10		-* Strongly-typed
11		-** Better suited for business "logic".
12		- E.g: Exploiting the compiler and IDE to catch exceptions at compile time rather than at run-time.
13		-* Uses Scala (functional) collection classes
	9	+** Immutable object model/graph
	10	+** Explicit transaction control
	11	+* Type Safety
	12	+** Better suited for database/business "logic".
	13	+ E.g: Exploits the compiler and IDE to catch exceptions at compile time rather than at run-time.
	14	+* Uses Scala Collections
14	14
15	15	= Migrating EOF -> Squeryl =
16	16
17		-In keeping with the strong-typed philosophy of Scala, Squeryl has no dynamic component like EOF (i.e an EO model file).
	18	+In contrast to EOF Squeryl maintains its ORM information programmatically - in the classes itself and collectively in a [[schema>>url:http://squeryl.org/schema-definition.html||shape="rect"]]. In keeping with the strongly-typed philosophy of Scala, Squeryl has no dynamic component like EOF (i.e an EO model file).
18	18
19		-EOF though has the ability to generate classes in Java (and in Objective-C prior to WebObjects 4.5) enforcing type as has become customary in enterprise environments. We may exploit this feature of EOF to generate a Squeryl schema.
	20	+EOF has the ability to generate classes in Java (and in Objective-C prior to WebObjects 4.5) because enforcing type has become customary in enterprise environments. We may exploit this feature of EOF to generate a Squeryl schema from an EO model.
20	20
21		-* Squeryl Templates
22		-** Entity.eotemplate [[template>>WOL:Squeryl _Entity.eotemplate]]
23		-** Entity.eotemplate [[template>>WOL:Squeryl Entity.eotemplate]]
	22	+=== Preparing your EO model ===
	23	+
	24	+* Make sure **all** EO entities have a class name (including abstract many-To-many "join" tables). FYI: There can be no support for entities classified as {{code language="none"}}EOGenericRecord{{/code}}.
	25	+* Mark the abstract many-To-Many join entities as {{code language="none"}}Abstract{{/code}}.
	26	+* (Temporary) Ensure all the model entities are in the same package. i.e the package is exclusive to the model.
	27	+
	28	+=== Generating the Squeryl Schema ===
	29	+
	30	+1. Create a .eogen file for your EO model as normal. Only set the {{code language="none"}}File Names{{/code}} extension to "scala".
	31	+1. Use the Squeryl EO Templates:
	32	+1*. _Entity.eotemplate [[template>>doc:WOL.Home.EOGenerator.EOGenerator Templates and Additions.Squeryl _Entity\.eotemplate.WebHome]]
	33	+1*. Entity.eotemplate [[template>>doc:WOL.Home.EOGenerator.EOGenerator Templates and Additions.Squeryl Entity\.eotemplate.WebHome]]
	34	+
	35	+{{note title="Note"}}
	36	+Any custom business "logic" will have to be manually re-written in Scala
	37	+{{/note}}
	38	+
	39	+== Differences Between a Squeryl Schema and EO Model/Classes ==
	40	+
	41	+* Optional attributes (i.e those that {{code language="none"}}allowsNull{{/code}}) are typed as {{code language="none"}}Option[WO:T]{{/code}}
	42	+* To one relationships that are not mandatory (i.e optional relationships) are also typed as {{code language="none"}}Option[WO:T]{{/code}}
	43	+* To many relationships are represented as a Squeryl iterable (collection class) as opposed to a {{code language="none"}}NSArray{{/code}}.
	44	+
	45	+=== Use of Scala Collections ===
	46	+
	47	+===== 1. Filtering =====
	48	+
	49	+Instead of using EOQualifiers to filter EOs dynamically, you can apply the type safe filter in Scala:
	50	+
	51	+{{code}}
	52	+
	53	+def activeFiles = files.filter(_.active == true)
	54	+
	55	+{{/code}}
	56	+
	57	+===== 2. Iteration =====
	58	+
	59	+Functional language iteration that's become increasingly popular can be used:
	60	+
	61	+{{code}}
	62	+
	63	+activeFiles.foreach(f => {
	64	+ ...
	65	+})
	66	+
	67	+{{/code}}
	68	+
	69	+===== 3. For-Comprehensions =====
	70	+
	71	+Here's just an example use of sequence comprehension:
	72	+
	73	+{{code}}
	74	+
	75	+def activeFiles = for (file <- files if file.active == true) yield file
	76	+
	77	+{{/code}}