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Technology sharing swift defense programming
2022-07-05 03:28:00 【Julie^_^ JuneLee】
1、 background
For developers to write code more effectively , Probability of preventing errors , We are in the process of code design and writing , Try to make sure your code doesn't make mistakes , Defensive programming enables us to find small problems as soon as possible , Instead of waiting until customers give feedback or receive abnormal crashes ?
As a developer , Few people can swear that their programs are 100% non bug, So moderate defense will improve development quality and reduce debugging bug Time for
An effective way to defend against coding :
- Once you encounter an agreed exception , The program must be compatible , You must not let the program Crash
- Once you encounter a predetermined exception , Just run out , If the upper layer does not deal with , be Crash
2、 Defensive programming habits
- 1.
If not necessary , Don't add entities or classes
: If you can do the same thing with fewer things , Then add more variables or entities 、 You need energy to maintain , It's also more likely to go wrong - 2.
Don't rush to write code
: Every line of code you start writing needs to think twice , Consider what kind of mistakes may occur , Consider all possible situations - 3.
Dispose of compilation warnings as much as possible
: Handling compilation warnings is a good habit , Compilation warnings may hide certain errors - 4.
Check all return values
: Check the return value of the method or property , Prevent exceptions - 5.
Use cast cautiously
: Cast needs to consider the input parameter type , Handle with care , Explain the coercion as clearly as possible - 6.
Check the boundary of the value
: For the value 、 The range of the array should be judged , Many lessons of historical collapse are caused by crossing the border
3、Swift Some points needing attention in
3.1、 optional type (Optional Type)
- Try to avoid declaring implicitly optional types , Unless it can be determined that it must have value when used
- Avoid using
as!
ortry!
Equal coercion , Use!
If abnormal, it will definitely lead to Crash - Be careful to use forced unpacking for optional variables , Optional default values can be used
The value of an optional variable , May be nil, If forced unpacking is used for optional variables , The context needs to be clear , Otherwise, there may be Crash
var test: String?
print(test) //nil
print(test!) //error、Crash
Better use , Use money to judge or use let Variable
if test != nil {
}
if let tempTest = test {
}
3.2 When multiple operators are combined , Use parentheses to prioritize
let flag = true || false && false
let flag1 = (true || false) && false
let flag2 = true || (false && false)
Print the results
flag = true
flag1 = false
flag2 = true
first line : The naked eye can't see who has a high level of operation
The second line : hold || Operations are enclosed in parentheses , Higher priority
The third line : hold && Operations are enclosed in parentheses , Higher priority
According to the printing results ,&& The priority ratio || high
3.3 Call in closure self Avoid circular references
Closures are commonly used , Will be [weak self] Put it in front of the closure parameter
testBlock() {
[weak self] name in
self?.doSomething()
}
4、swift Some specifications in
1. Use as much as possible
let
, Be able to use let You don't have to var2. When declaring class methods and properties , priority of use
static
Instead ofclass
3. If the function has no arguments , The function body is simple , Only some objects or values are fed back , It is recommended to use calculated properties
struct Square { var side: CGFloat = 2.0 // recommend var girth: CGFloat { return side * 4 } // Not recommended // func girth() -> CGFloat { // return side * 4 // } // recommend func halfGirth() -> CGFloat { self.side = side * 0.5 return side * 4 } // Not recommended // var halfGirth: CGFloat { // self.side = side * 0.5 // return side * 4 // }
4. Enumerating using the preferred set switch When the sentence is , Do not include default, conversely ,switch You need to use default Including other situations
5. When expanding optional parameters , Recommended
guard
sentence , instead ofif
sentence , Reduce code nesting or indentation 、 Increase code readability// recommend guard let tempTest = test else { return } doSomething(on: tempTest) // Not recommended if let tempTest = test { doSomething(on: tempTest) } //
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