1 Introduction
The purpose of this page is to give a quick overview of how to compose component hierarchies using the PEAK framework, using working code. I have inlined comments in the code example, so hopefully, it will be self explanatory.
2 Code
Here's the code example that I came up with while working out how to compose hiearchies, and "aquire" objects from parent components in PEAK. It requires the current CVS version of PEAK (0.5a3).
1 #file components1.py
2 from peak.api import *
3
4 SPAM_PROPERTY = PropertyName("simplecmpApp.spam")
5 COLOR_PROPERTY = PropertyName("simplecmpApp.color")
6 EGGS_PROPERTY = PropertyName("simplecmpApp.eggs")
7
8
9 #------------------------------------------------------------
10 class ISpam(protocols.Interface):
11 """Spam interface"""
12 def spam():
13 """provide spam"""
14
15 class Spam(binding.Component):
16 protocols.advise(instancesProvide=[ISpam])
17 def spam(self):
18 return "spam"
19
20 #------------------------------------------------------------
21 class IEggs(protocols.Interface):
22 """Eggs interface"""
23 def eggs():
24 """provide eggs"""
25
26 class Eggs(binding.Component):
27 protocols.advise(instancesProvide=[IEggs])
28 def eggs(self):
29 return "eggs"
30
31 class OtherEggs(binding.Component):
32 protocols.advise(instancesProvide=[IEggs])
33 def eggs(self):
34 return "othereggs"
35
36
37 #------------------------------------------------------------
38 class GrandChildCmp(binding.Component):
39 #acquired from SimpleCmp
40 gcSpam = binding.Obtain(SPAM_PROPERTY)
41 gcColor = binding.Obtain(COLOR_PROPERTY)
42 gcEggs = binding.Obtain(EGGS_PROPERTY)
43 #acquired from ChildCmp
44 gcOtherEggs = binding.Obtain(IEggs)
45 #acquired from SimpleCmp
46 gcStr = binding.Obtain("sc_string")
47
48 class ChildCmp(binding.Component):
49 #acquired from SimpleCmp
50 cSpam = binding.Obtain(ISpam)
51 cStr = binding.Obtain("sc_string")
52 #overrides IEggs provided by SimpleCmp
53 cEggs = binding.Obtain(IEggs)
54 __eggs = binding.Make(OtherEggs, offerAs=[IEggs])
55
56 #make a GrandChild child of this component
57 grandChild = binding.Make(GrandChildCmp)
58
59 class SimpleCmp(binding.Component):
60 #simple component variable. Child components can look up directly by name
61 sc_string = "simple-c!"
62 #__eggs and __spam are registered as Interfaces and properties
63 #They can be bound either using binding.Obtain(<InterfaceName>)
64 #or binding.Obtain(PropertyName(<property.name>))
65 __eggs = binding.Make(Eggs, offerAs=[IEggs, EGGS_PROPERTY])
66 __spam = binding.Make(Spam, offerAs=[ISpam, SPAM_PROPERTY])
67 #__color is a Constant bound to a property
68 __color = binding.Make(lambda:"red", offerAs=[COLOR_PROPERTY])
69
70 #make a ChildCmp child of this component
71 child = binding.Make(ChildCmp)
72
73 #------------------------------------------------------------
74 if __name__ == "__main__":
75
76 sc = SimpleCmp()
77 c = sc.child
78 gc = c.grandChild
79
80
81 print "c.eggs: ",c.cEggs.eggs()
82 print "c.spam: ",c.cSpam.spam()
83 print "c.cStr: ",c.cStr
84 print "gc.spam: ",gc.gcSpam.spam()
85 print "gc.eggs: ",gc.gcEggs.eggs()
86 print "gcOther.eggs: ",gc.gcOtherEggs.eggs()
87 print "gc.myColor: ",gc.gcColor
88 print "gc.gcStr: ",gc.gcStr
89 print "done"
3 Running the example
Running this example should produce output similar to below:
[joel@banzai playground1]$ python components1.py
c.eggs: othereggs
c.spam: spam
c.cStr: simple-c!
gc.spam: spam
gc.eggs: eggs
gcOther.eggs: othereggs
gc.myColor: red
gc.gcStr: simple-c!
done
--Joel Boehland
