The beauty of do end usage

Why use do end, What problems can it solve ; First , Statement block is not used Curly braces { } , It is do Sentence block end Indicates the beginning and end of a statement block . and Curly braces {} It means a Table structure .

do-end blocks It solves the problem of variable scope , First of all, we must understand local Variables and global variables have completely different lexical scopes ; We should try to state local Variable , Try to reduce the scope of a variable , Make it only exist in the variable block you need , Instead of polluting the wider public environment ;

First, let's refer to two examples ：

do
    local x1=1
    local x2=2
    local sum=x1+x2
end
print(x1,x2) --nil    nil

No, do end：

local x1=1
local x2=2
local sum=x1+x2
print(x1,x2) --1    2

stay Lua in , Use do-end Wrap one or more statements as a statement block （block）, Form a scope , Local variables defined in this scope are only valid in the current scope , After being out of scope, it will be automatically recycled by the garbage collector ！

do
	local l_var = 1  --  local variable 
	g_var = 2  --  Global variables 
	print(l_var, g_var)  -- 1	2
end
print(l_var, g_var)  -- nil	2

Global variables defined in the scope are not affected by the scope ！