类型转换错误

Question

I am trying to follow the tutorial here : https://goethereumbook.org/block-query/

In his code , he calls the header and then hard codes it into blockNumber.

 header, err := client.HeaderByNumber(context.Background(), nil)
    if err != nil {
        log.Fatal(err)
    }

    fmt.Println(header.Number.String()) // 5671744

    blockNumber := big.NewInt(5671744)

I have attempted to improve on this and converted the string to int64.

header, err := client.HeaderByNumber(context.Background(), nil)
    if err != nil {
        log.Fatal(err)
    }

    fmt.Println(header.Number.String())

    var stringBlockNumber = header.Number.String()

    int64BlockNumber, err := strconv.ParseInt(stringBlockNumber, 10, 64)
    if err != nil {
        log.Fatal(err)
    }

    blockNumber := big.NewInt(int64BlockNumber)

    block, err := client.BlockByNumber(context.Background(), blockNumber)
    if err != nil {
        log.Fatal(err)
    }

This works until in try to add the following line:

fmt.Println(block.Number.Uint64())

I get the following error in the terminal :

./queryBlock.go:41:26: block.Number.Uint64 undefined (type func() *big.Int has no field or method Uint64)

I would appreciate any pointers on this.

Answer 1

After getting the block by number through client.BlockByNumber, block is of type Block from /github.com/ethereum/go-ethereum/core/types.

Number of Block is a method, which returns a *big.Int instead of being a field of that type. So To retrieve the number, you should call the method, i.e, block.Number().