Lua编程示例(二):面向对象、metatable对表进行扩展

时间:2022-10-17 16:12:55
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counter = {
 count = 0
}
function counter.get(self)
 return self.count
end
 
function counter:inc()
 self.count=self.count+1
end
 
print(counter.get(counter))
counter.inc(counter)
print(counter.get(counter))
 
counter2={
 count=4,
 get = counter.get,
 inc = counter.inc,
}
 
print(counter2:get())
counter.inc(counter2)
print(counter2.get(counter2))
 
print()
 
tb1 ={ "alpha","beta","gamma"}
mt={}
setmetatable(tb1,mt)
 
print(getmetatable(tb1) == mt)
 
print()
 
function mt.__add(a,b)
 local result = setmetatable({},mt)
 for i=1,#a do
 table.insert(result,a[i])
 end
 for i=1,#b do
 table.insert(result,b[i])
 end
 return result
end
 
tb2={"aaa","bbb","ccc"}
res=tb1+tb2
for i,v in ipairs(res) do
 print(v)
end
print()
function mt.__unm(a)
 local result = setmetatable({},mt)
 for i=#a , 1 ,-1 do
 table.insert(result,a[i])
 end
 return result
end
 
res=-tb1+tb2
for i,v in ipairs(res) do
 print(v)
end
 
print()
function mt.__tostring(a)
 local result = "{"
 for i,v in ipairs(a) do
 result = result.." "..v
 end
 result = result.." } "
 return result
end
 
print(tb1)
 
function mt.__index(tb1,key)
 print("there is no "..key.." in the table")
 return nil
end
 
print(tb1["fsy"])
 
function mt.__newindex(a,key,v)
 if( key == "haha") then
 error(" Stop laugh!",2)
 else
 rawset(a,key,v)
 end
end
 
tb1.haha="heihei"

 
运行结果:

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0
1
4
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true
 
alpha
beta
gamma
aaa
bbb
ccc
 
gamma
beta
alpha
aaa
bbb
ccc
 
{ alpha beta gamma }
there is no fsy in the table
nil
lua: my_test.lua:166: Stop laugh!
stack traceback:
 [C]: in function 'error'
 my_test.lua:160: in function <my_test.lua:158>
 my_test.lua:166: in main chunk
 [C]: ?