我目前正在尝试调试具有功能和API功能的基于Minecraft的龟养殖脚本。
当我执行时，我得到一个'io'异常（这是可以理解的，因为我试图为每个循环写一个日志），但是它没有告诉我它在哪个脚本中或行号。除了在整个程序执行过程中进行打印以外，还有其他解决方案吗？
我得到的异常：
io:107: index expected, got nil
主要的乌龟养殖脚本：
--[[main script for farming procedure]]
--load functions responsible for positioning/repositioning/farming
os.loadAPI("APIS/positioners");
os.loadAPI("APIS/farmers");
--action turtle start farming condition
assert(positioners.check_start_pos(), "Could not initialise the turtle for the farming procedure\nCould not identify it's starting location\n(are there birch planks directly above and beneath it?");
--check Netherrack can be found from start block, declare 'dir' also as local
local init_result, dir = positioners.find_next_neth()
assert(init_result, "Could not find the appropriate direction to travel in from\n the turtle starting position, is the farm set up correctly?");
local loop_vars = {["count"] = 0, ["blockId"] = nil, ["dir"] = nil, ["prevManvr"] = nil, ["action"] = ""};
--**input** assertion tests for required fuel level and seed requirements
assert(turtle.getFuelLevel() > 50, "Fuel level is below required level to start farming, - terminating");
--given 'result' == true can start farming
turtle.forward();
--open log file (overwrite) and save to io class handle
log = io.open("logs/proc_log", "w");
--start main farming process loop
while turtle.getFuelLevel() > 0 do
--reset action variable
loop_vars["action"] = "";
--sort log variables
loop_vars["count"] = loop_vars["count"] + 1;
--identify the block above (returns inv slot(1-4) it matches with or false if it doesn't)
loop_vars["blockId"] = positioners.id();
if blockId == 1 then
loop_vars["action"] = "Netherrack above ";
if loop_vars["dir"] == nil then
print("Netherrack found, planting");
farmers.plant();
--shift turtle forward such that it can evaluate a new block. Ensure that moves forward in case of obstruction
assert(turtle.forward(), "The turtle is impeded from moving forwards in farming route");
--log statement
loop_vars["action"] = loop_vars["action"].."plant and move forward";
else
--initiate change in direction procedure
assert(positioners.change_direction(loop_vars["dir"]), "Failed to complete turtle change direction procedure");
--reset dir
loop_vars["dir"] = nil;
loop_vars["action"] = loop_vars["action"].." actioned 'positioners.change_position(dir)'.";
end;
elseif blockId == 3 then
turtle.forward();
--log statement
loop_vars["action"] = "Proceeding past marble block";
elseif blockId == false then
print("Finding next Netherrack block.");
--retrace back to the most recent 'legitimate' block");
turtle.back();
--call function to reposition turtle for next farming line
result, loop_vars["dir"] = positioners.find_next_neth(loop_vars["prevMan"]);
assert(result, "A new netherrack block could not be found in any direction.");
--assign dir result to prevMan (information for next positioners.change_position() call
loop_vars["prevMan"] = loop_vars["dir"];
--log statement
loop_vars["action"] = "No 'legitimate' block above, 'positioners.find_next_neth() successful,\nassigning dir accordingly.";
else
--log statement
log.write("Unhandled exception in farm_proc main loop");
log.close();
error("positioners.find_next_neth() did not find an appropriate block above it.");
end;
print("farm_proc loop");
--write current turn to log file
log.write("Turn no: "..loop_vars["count"].."\n Id()== "..tostring(loop_vars["blockId"]).."\n Action: "..loop_vars["action"].."\n Previous maneuver: "..loop_vars["prevMan"].."\n\n");
end;
--updating log
log.write("Error - turtle ran out of fuel\n");
log.close();
error("Turtle ran out of fuel whilst planting - terminated");
“定位器” api（基于运动/检测的任务）：
function find_next_neth(prevMan)
--[[Find direction of the next overhead block of Netherrack from turtle's current pos,
Order;
N
E
W
S
Error (no direction found)]]
--define numbers corresponding to directions
local dirs = {"Back", "Left", "Right", "Forward"};
--create a loop counter to ensure does not exceed full checking loop
local counter = 4;
--loop through movement proc. until netherrack (slot 1) is found above it (if at all)
while true do
print("Looping, current loop counter is: ", counter);
local idAhead = id_ahead();
if counter == 4 then
--placeholder, script should never need to find forwards
elseif counter == 3 then
turtle.turnLeft();
elseif counter == 2 then
turtle.turnRight();
turtle.turnRight();
elseif counter == 1 then
turtle.turnRight();
--decremented counter has reached it's minimum
elseif counter < 1 then
return false, nil;
else
error("For find_next_neth iteration counter out of range");
end;
--decrement counter variable
counter = counter - 1;
--boolean condition to determine whether function is complete, incomplete or broken. 'prevMan' as a logical statement will return true if var has value, and false if not
local testPrev = (not prevMan == dir[(math.abs(counter - 4) + 1))] or not prevMan);
local validBlock = (idAhead == 1 or idAhead == 3)
if testPrev and validBlock then
--all tests are valid - break loop to return
break;
end;
--report success and return result
print("Nether found!\n");
return true, dirs[counter];
end;
end;
function change_direction(dir)
--intialise a base error string
local errMsg = "Could not action positioners.change_direction(dir, prevMan) ";
if dir == "East" then
assert(turtle.forward(), errMsg.."Obstruction to route");
--this should finalise a 180deg turn to the left
turtle.turnLeft()
elseif dir == "West" then
assert(turtle.forward(), errMsg.."Obstruction to route");
--180deg turn left
turtle.turnRight()
elseif dir == "North" then
--no action
elseif dir == "South" then
error("Return to start not yet implemented");
else
error("positioners.change_direction() parameter not as expected");
end;
return true;
end;
function id(slot)
--[[Determines if netherrack is currently above turtle.
Return false means the block
above does not match slots 1-4 of the
turtle's inv. Takes optional int
for specific block slot index
in turtle compare]]
--checking argument
if slot ~= nil then
--select slot given as argument
turtle.select(slot);
if turtle.compareUp() then
--don't return int because specific material requested
return true;
else
return false;
end;
end;
counter = 1
while counter < 5 do
turtle.select(counter);
--identify whether the current selected slot item matches the blovk overhead
if turtle.compareUp() then
--return block above's corresponding slot index
return counter
end;
counter = counter + 1;
end;
--return number indicating unidentfied block
return false;
end;
function id_ahead(slot)
if turtle.forward() then
--save value of id call for later return
local rtn = id(slot)
turtle.back();
return rtn
else
error("turtle could not move forwards in id_ahead(slot)");
end;
end;
function check_start_pos()
--set selected slot to birch planks (no currently selected method implemented so cannot revert this change internally)
turtle.select(2);
--save boolean variables for comparison of blocks above and below position
local up = turtle.compareUp();
local down = turtle.compareDown();
--test if above boolean values are true (turtle in designated start position)
if up and down then
return true;
else
print("Not in appropriate farming start position");
return false;
end;
end;
（“农民” API只是检查当前的种子，然后通过Farmers.plant（）种植农作物