OrderCheck HOW

Example from file: examples/demos/lowlevel/02_trading_operations.go

The OrderCheck() method performs a safe preliminary validation of an order before sending it. It allows you to verify that the order parameters are correct and that the account has sufficient funds to open it.

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🧩 Code example

fmt.Println("\n3.1. OrderCheck() - Validate order parameters")

// The filling mode must be one the symbol allows (SYMBOL_FILLING_MODE flags: 1 = FOK, 2 = IOC);
// with a mode the symbol does not allow, the check fails.
typeFilling := pb.MRPC_ENUM_ORDER_TYPE_FILLING_ORDER_FILLING_RETURN
fillingData, err := account.SymbolInfoInteger(ctx, &pb.SymbolInfoIntegerRequest{
    Symbol: cfg.TestSymbol,
    Type:   pb.SymbolInfoIntegerProperty_SYMBOL_FILLING_MODE,
})
if err == nil {
    if fillingData.Value&1 != 0 {
        typeFilling = pb.MRPC_ENUM_ORDER_TYPE_FILLING_ORDER_FILLING_FOK
    } else if fillingData.Value&2 != 0 {
        typeFilling = pb.MRPC_ENUM_ORDER_TYPE_FILLING_ORDER_FILLING_IOC
    }
}

orderCheckReq := &pb.OrderCheckRequest{
    MqlTradeRequest: &pb.MrpcMqlTradeRequest{
        Action:      pb.MRPC_ENUM_TRADE_REQUEST_ACTIONS_TRADE_ACTION_DEAL,
        Symbol:      cfg.TestSymbol,
        Volume:      cfg.TestVolume,
        OrderType:   pb.ENUM_ORDER_TYPE_TF_ORDER_TYPE_TF_BUY,
        Price:       tickData.Ask,
        StopLoss:    0.0,
        TakeProfit:  0.0,
        Deviation:   10,
        TypeFilling: typeFilling, // a filling mode the symbol allows
        TypeTime:    pb.MRPC_ENUM_ORDER_TYPE_TIME_ORDER_TIME_GTC,
        Comment:     "OrderCheck validation",
    },
}

checkData, err := account.OrderCheck(ctx, orderCheckReq)
if err != nil {
    fmt.Println("  ❌ OrderCheck FAILED")
    fmt.Printf("     Error: %v\n", err)
} else if checkData != nil && checkData.MqlTradeCheckResult != nil {
    result := checkData.MqlTradeCheckResult
    fmt.Println("  ✅ OrderCheck SUCCESS!")
    fmt.Printf("     Return Code:        %d\n", result.ReturnedCode)
    fmt.Printf("     Comment:            %s\n", result.Comment)
    fmt.Printf("     Required Margin:    %.2f\n", result.Margin)
    fmt.Printf("     Balance After:      %.2f\n", result.BalanceAfterDeal)
    fmt.Printf("     Equity After:       %.2f\n", result.EquityAfterDeal)
    fmt.Printf("     Free Margin After:  %.2f\n", result.FreeMargin)
    fmt.Printf("     Margin Level:       %.2f%%\n\n", result.MarginLevel)

    // OrderCheck returns 0 on successful validation (unlike OrderSend which returns 10009)
    if result.ReturnedCode == 0 {
        fmt.Println("  ✓ Order validation PASSED – safe to proceed with OrderSend()")
    } else {
        // Use helper from errors.go to get human-readable error description
        fmt.Printf("  ⚠️  Validation failed: %s (code: %d)\n",
            mt5.GetRetCodeMessage(uint32(result.ReturnedCode)),
            result.ReturnedCode)
    }
}

---

🟢 Detailed Code Explanation

1️. Form the Request Structure

orderCheckReq := &pb.OrderCheckRequest{ MqlTradeRequest: &pb.MrpcMqlTradeRequest{ ... } }

A request object is created, containing the MqlTradeRequest structure — a complete description of the order, as if it were actually being sent to MetaTrader.

Key fields:

• Action – trade action type (TRADE_ACTION_DEAL — execute immediately);
• Symbol – instrument (cfg.TestSymbol from config.json);
• Volume – order volume;
• OrderType – direction (BUY or SELL);
• Price – opening price;
• Deviation – allowable price deviation in points;
• TypeFilling – execution mode. It must be one the symbol allows: the demo reads SYMBOL_FILLING_MODE (flags 1 = FOK Fill-Or-Kill, 2 = IOC Immediate-Or-Cancel) and picks an allowed one. A mode the symbol does not allow makes the check fail (e.g. IOC on a FOK-only symbol: ERR_TRADE_SEND_FAILED);
• TypeTime – order lifetime (GTC – Good Till Cancelled).

---

2️. Send Validation Request

checkData, err := account.OrderCheck(ctx, orderCheckReq)

The gateway passes the request to MetaTrader, which validates the order for correctness and returns the result — without actually opening a position.

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3️. Process the Result

If there is an error (err != nil), the check did not pass (MetaTrader's OrderCheck failed, e.g. not enough money or invalid stops) or the call itself failed; the error (*mt5.ApiError) carries the trade return code and its description. If a result is received, the validation fields are displayed:

result := checkData.MqlTradeCheckResult
fmt.Printf("     Required Margin:    %.2f\n", result.Margin)
fmt.Printf("     Free Margin After:  %.2f\n", result.FreeMargin)
fmt.Printf("     Margin Level:       %.2f%%\n", result.MarginLevel)

• Margin – how much margin will be required for the trade;
• FreeMargin – how much free margin will remain after opening;
• MarginLevel – margin level as a percentage.

---

4️. Interpret the Result

// OrderCheck returns 0 on successful validation (unlike OrderSend which returns 10009)
if result.ReturnedCode == 0 {
    fmt.Println("  ✓ Order validation PASSED – safe to proceed with OrderSend()")
} else {
    // Use helper from errors.go to get human-readable error description
    fmt.Printf("  ⚠️  Validation failed: %s (code: %d)\n",
        mt5.GetRetCodeMessage(uint32(result.ReturnedCode)),
        result.ReturnedCode)
}

Important: OrderCheck uses different success code than trading operations

1. OrderCheck success: ReturnedCode == 0 means validation passed
2. Trading operations success: ReturnedCode == 10009 (checked with mt5.IsRetCodeSuccess())

Why use mt5.GetRetCodeMessage() for errors?

1. Automatic Error Descriptions: Instead of just showing a number, get human-readable messages for common validation errors:
2. TRADE_RETCODE_INVALID_VOLUME - Volume doesn't meet broker requirements
3. TRADE_RETCODE_NO_MONEY - Insufficient funds for the trade
4. TRADE_RETCODE_INVALID_STOPS - SL/TP levels violate broker rules
5. TRADE_RETCODE_INVALID_PRICE - Price out of valid range
6. Consistency: Same error handling pattern used across all trading operations
7. Centralized: All 40+ error codes defined in package/Helpers/errors.go

If ReturnedCode == 0 → the order passed validation and it's safe to proceed with OrderSend(). Any other value indicates a validation error that should be fixed before attempting to send the order.

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📦 What the Server Returns

message OrderCheckData {
  MrpcMqlTradeCheckResult MqlTradeCheckResult = 1;
}

message MrpcMqlTradeCheckResult {
  uint32 ReturnedCode = 1;
  double BalanceAfterDeal = 2;
  double EquityAfterDeal = 3;
  double Profit = 4;
  double Margin = 5;
  double FreeMargin = 6;
  double MarginLevel = 7;
  string Comment = 8;
}

---

💡 Example Output

✅ OrderCheck SUCCESS!
     Return Code:        0
     Comment:            Done
     Required Margin:    120.50
     Balance After:      9879.50
     Equity After:       9879.50
     Free Margin After:  9759.00
     Margin Level:       1120.75%

✓ Order validation PASSED – safe to proceed with OrderSend()

---

🧠 What It's Used For

The OrderCheck() method is used for:

• validating order correctness before sending;
• assessing future account state after the trade;
• protection from errors and broker rejections;
• safe testing of strategies and robots.

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💬 In Simple Terms

OrderCheck() is a "rehearsal" before a trade. It checks whether an order with the specified parameters can be opened, and how balance, margin, and equity will change after the trade. If everything is correct (code 0) — you can safely proceed with OrderSend().