際際滷

Code Refactoring
THAY ??I NH? - L?I ?CH L?N

N?i dung
? T?i sao c?n code refactoring
? M? b?n
? C│c k? thu?t refactoring
? Demo

Tuy┷n ng?n Agile
Ch┣ng t?i ?? ph│t hi?n ra c│ch ph│t tri?n ph?n m?m t?t h?n b?ng c│ch th?c
hi?n n┏ v┐ gi┣p ?? ng??i 一鞄│界 th?c hi?n. Qua c?ng vi?c n┐y, ch┣ng t?i ?? ?i ??n vi?c
?│nh gi│ cao:
C│ nh?n v┐ s? t??ng t│c h?n l┐ quy tr━nh v┐ c?ng c?;
Ph?n m?m ch?y t?t h?n l┐ t┐i li?u ??y ??;
C?ng t│cv?i 一鞄│界h h┐ng h?n l┐ ?┐m ph│n h?p ??ng;
Ph?n h?i v?i c│c thay ??ih?n l┐ b│m s│t k? ho?ch.
M?c d┫ c│c ?i?u b┷n ph?i v?n c┛n gi│ tr?, nh?ng ch┣ng t?i ?│nh gi│ cao h?n c│c m?c ? b┷n tr│i.
AgileAlliance.org

Chuy?n giao nhanh
Th?i gian
´
Iteration

Design is the key,
Planned Design is not ´
? Takeuchi & Nonaka: overlapping is better than sequential
Not efficient:
? Time consuming
? No backward
? No ＾better idea￣ on the go
L┐m th? n┐o ?? t? ch?c ki?u ＾Overlapping￣ nh? th? n┐y?

Simple Design l┐ g━?
? Design s? ti?n ho│ theo qu│ tr━nh
? KH?NG c?n c┏ design to┐n b? t? ??u. V?a ?? th?i
? L┐ m?t ph?n c?a quy tr━nh ph│t tri?n
? Ch??ng tr━nh l?n l┷n th━ design s? thay ??i theo
? Kh?ng ph?i l┐ chi?n thu?t ＾code and fix￣
7
Evolve

Simplicity
Rationale behind Simple Design
? ￣T?o ra th? ??n gi?n nh?t c┏ th? ch?y ???c＾
? ￣Ch┣ng ta s? kh?ng bao gi? c?n t?i n┏＾
? ??u t? cho m?u thi?t k?
? H? th?ng t?i gi?n
1. Ch?y to┐n b? test
2. R? m?c ?┴ch
3. Kh?ng tr┫ng l?p
4. C┏ ┴t l?p v┐ ph??ng th?c nh?t c┏ th?
8

Thi?t k? ?? Giao ti?p
? V? thi?t k? ra ?? th?o lu?n trong nh┏m
? Ch? c?n ?? ?? l┐m r? gi?i ph│p
? Ch? n┷n s? d?ng c│c l?u ?? ??n gi?n, kh?ng m?t nhi?u c?ng
duy tr━
? Gi? minh b?ch c│c l?u ??
? Treo ? t??ng
? Khuy?n kh┴ch m?i ng??i c?p nh?t
? ?? ? xem li?u m?i ng??i c┏ d┫ng kh?ng, hay l┐ v?t x┏
9

Thi?t k? ?? X?y d?ng
? ＾Ph?n m?m ch?y t?t l┐ th??c ?o ch┴nh v? ti?n ??￣
? Thi?t k? s? ???c chuy?n th┐nh t┴nh n?ng ch?y ???c, do ?┏:
? Design ph?i chia ra ?? code ???c trong nh┏m
? Ph?n t│ch, interface, giao ti?p gi?a c│c th┐nh ph?n
? Design ph?i ki?m th? ???c
? ＾Ki?n tr┣c s? c?n ph?i code￣
10

Refactoring
? ?? c┏ thi?t k? ??n gi?n h?n
? Duy tr━, c?p nh?t d? h?n
? L┐ m?t vi?c b?t bu?c ph?i l┐m
? ?? ? ??n m?u thi?t k? v┐ c│c best practices
11
Image: http://www.testically.org

T│i c?u tr┣c m? ngu?n
? T│i c?u tr┣c m? ngu?n l┐ c│c k? thu?t cho ph└p ch?nh s?a m?
ngu?n n?i b? m┐ kh?ng l┐m thay ??i h┐nh vi c?a h? th?ng ??i
v?i b┷n ngo┐i
? T│i c?u tr┣c m? ngu?n nh?m m?c ?┴ch ch┴nh:
? M? ngu?n d? duy tr━ h?n
? M? ngu?n d? m? r?ng h?n
L?u ?: T│i c?u tr┣c m? ngu?n kh?ng ph?i lu?n lu?n gi┣p t?ng hi?u n?ng
(performance) c?a thu?t 岳看│稼. Trong m?t s? tr??ng h?p, c┏ th? c?n hy sinh hi?u
n?ng ?? c┏ ???c m? ngu?n t?t h?n

Development Flow
Requirement
Analysis
UI Mocking
?Customer
discussion
Design Draft
?Design
Discussion
Code the
skeleton to
test the
design
Coding in
team
Refactoring
and
Refinement
Build the
increment
$
DevTeamPO
Collaboration:
Steps:
Artifacts:
As a super user,
I want to ´
A
B
IDo
Interface IDo{
//TODO ´
}
Class A{
//TODO ´
}
Class B:IDo{
//TODO ´
}
Interface IDo{
//TODO ´
}
Class A{
method1(){
//Mr. A codes here
}
}
Class B:IDo{
method1(){
//Mrs. B codes here
}
}
Class C{
}
$
PO

Ti?n ho│ c?a c│c Model
com.myapp.Models
com.myapp.Views
com.myapp.Controllers
Sprint 0
updated story
V1
M1
IDo
C1
V1
M1
IDo
C1
V2
M2
Sprint 1 Sprint 2
Product
Backlog
Items burnt
Items burnt
Initial Architecture Model1 Model 2

＾Continuous￣ Architecting
Sprint #1: without layering
Presentation
Tier
Application
Layer
Business Layer
Data Access
Layer
Data Tier

Sprint #2: refactoring to layers
16
Presentation Tier
Application
Layer
Business Layer
Data Access
Layer
Data Tier

Sprint #3: architecting ＾on the go￣
17
Presentation Tier Application Layer Business Layer Data Access Layer Data Tier

Ph??ng th?c d┐i qu│
D?u hi?u:
? Qu│ nhi?u d┛ng code
? C┏ qu│ nhi?u t?ng code
? ?? ph?c t?p cao
X? l?:
? T│ch ph??ng th?c
? S? d?ng Parameter Object
? Ph?n t│ch c│c kh?i l?nh ?i?u
ki?n
19

L?p to qu│
D?u hi?u:
? C┏ qu│ nhi?u tr??ng
? C┏ qu│ nhi?u ph??ng th?c
? C┏ qu│ nhi?u d┛ng code
X? l?:
? T│ch l?p
? T│ch l?p con
? T│ch interface
20

Danh s│ch tham s? d┐i qu│
D?u hi?u:
? C┏ nhi?u h?n 3 ho?c 4 tham
s? cho m?t ph??ng th?c
X? l?:
? Thay th? tham s? b?ng l?i g?i
ph??ng th?c
? Gi? nguy┷n object
? Truy?n v┐o ??i t??ng
21

M? b? l?p
D?u hi?u:
? Hai ho?c nhi?u ?o?n m? nh━n
g?n gi?ng nhau
X? l?:
? T│ch l?p cha
? Chuy?n th┐nh template method
? Thay th? thu?t 岳看│稼
22

Ghi ch┣
D?u hi?u:
? C┏ nhi?u ghi ch┣ ?? gi?i th┴ch
c│c ?o?n m?
X? l?:
? T│ch bi?n
? Thay ??i t┷n ph??ng th?c
23

M?t s? k? thu?t t│i c?u tr┣c
K? thu?t ??i t┷n bi?n
K? thu?t ??i t┷n ph??ng th?c
K? thu?t t│ch bi?n
K? thu?t t│ch h?ng
K? thu?t t│ch ph??ng th?c

??i t┷n bi?n v┐ ph??ng th?c
? Thay ??i t┷n bi?n ho?c ph??ng th?c ?? tr? n┷n t?t h?n: d?
??c, c┏ ? ngh?a, th? hi?n ???c ? ngh?a, tu?n th? coding
convention
? Khi ??i t┷n bi?n ho?c ph??ng th?c c?n l?u ?:
? ??i t┷n t?i v? tr┴ khai b│o
? ??i t┷n t?i t?t c? c│c v? tr┴ c┏ s? d?ng bi?n ho?c ph??ng th?c
? N┷n s? d?ng t┴nh n?ng c?a IDE ?? ??i t┷n bi?n ho?c ph??ng
th?c

T│ch bi?n
? Trong nhi?u tr??ng h?p, c│c bi?u th?c ph?c t?p s? g?y kh┏
hi?u
? T│ch bi?n (Variable Extraction) l┐ k? thu?t gi┣p ??n gi?n ho│
c│c bi?u th?c v┐ gi┣p d? hi?u h?n

Code Refactoring: Thay ??i nh? - L?i ┴ch l?n

T│ch bi?n: V┴ d? ki?m tra n?m nhu?n
function isLeapYear(year) {
if(year % 4 == 0){
if (year % 100 == 0){
if(year % 400 == 0)
return true;
} else {
return true;
}
}
return false;
}
varr isDivisibleBy4 = year % 4 == 0;
if(isDivisibleBy4){
if (isDivisibleBy100){
if(isDivisibleBy400)
return true;
} else {
return true;
}
}
return false;
}

T│ch h?ng
? Trong nhi?u tr??ng h?p, c│c gi│ tr? ＾th?n k?￣ (magic value) s?
g?y kh┏ kh?n cho vi?c ??c hi?u m? ngu?n
? T│ch h?ng gi┣p mang l?i ? ngh?a cho c│c gi│ tr? ＾th?n k?￣ v┐ m?
ngu?n d? hi?u h?n

T│ch h?ng: V┴ d? ph?n quy?n d?a v┐o
role
function isAuthorized(var role){
if(role == 1){
return true;
}
return false;
}
const ROLE_ADMIN = 1;
function isAuthorized(role){
if(role == ROLE_ADMIN){
return true;
}
return false;
}

T│ch ph??ng th?c
? Trong nhi?u tr??ng h?p, m?t ph??ng th?c qu│ d┐i, qu│ ph?c
t?p ho?c x? l? qu│ nhi?u t│c v? s? d?n ??n kh┏ hi?u, kh┏ ki?m
so│t
? T│ch ph??ng th?c gi┣p cho c│c ph??ng th?c d? ??c hi?u h?n,
d? ki?m so│t h?n

T│ch ph??ng th?c: V┴ d? t┴nh s? ng┐y
function getDaysOfMonth(month, year){
switch (month){
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
return 31;
case 4:
case 6:
case 9:
case 11:
return 30;
´
case 2:
var isLeapYear = false;
if(year % 4 == 0){
if (year % 100 == 0){
if(year % 400 == 0)
isLeapYear = true;
} else {
isLeapYear = true;
}
}
if(isLeapYear){
return 29;
} else {
return 28;
}
default:
return 0;
}

Refactoring to Patterns
? Strategy
? Decorator
? Command
? Template Method
? Abstract Builder
? ´

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Code Refactoring: Thay ??i nh? - L?i ┴ch l?n

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