Expert Advisor Programming by Andrew R. Young

Tips and Tricks
string SettingsComment = "FastMAPeriod: "+FastMAPeriod+" SlowMAPeriod: "+SlowMAPeriod;
string StatusComment = "Buy order placed";
Comment(SettingsComment+"\n"+StatusComment);
We declare and set the values of the SettingsComment
and StatusComment strings inside the start()
function. At the end of the start function, we call the
Comment() function and use it to print our comments to
the chart. We use a newline character (\n) to separate
the comments into two lines.
Fig 8.1: Chart comment using a newline character
Check Settings
There are several expert advisor properties that must be enabled before the expert advisor may be
allowed to trade. These settings are located under the Common tab in the Expert Properties dialog.
The setting Allow live trading must be enabled before trading can commence. If it is not enabled, a
frowning face will appear in the top right hand corner of the chart, next to the expert advisor name.
You can check for this condition in your EA by using the IsTradeAllowed() function. If it returns
false, the setting Allow live trading is disabled.
If you'd like to display a message to the user indicating that this setting should be activated, you can
do as follows:
if(IsTradeAllowed() == false) Alert("Enable the setting \'Allow live trading\' in the
Expert Properties!");
If your expert advisor uses an external .ex4 library, the setting Allow import of external experts must
be enabled in the Expert Properties. You can check for this using the IsLibrariesAllowed()
function:
if(IsLibrariesAllowed() == false) Alert("Enable the setting \'Allow import of external
experts\' in the Expert Properties!");
The same thing can be done for DLLs using the IsDllsAllowed() function:
if(IsDllsAllowed() == false) Alert("Enable the setting \'Allow DLL imports\' in the
Expert Properties!");
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