I get this error when I try to Marshall an object of nested structs. My structs look like:
type Blockchain struct{
blocks []Block `json:"blocks"`
difficulty int `json:"difficulty"`
}
type Block struct{
index int `json:"index"`
timestamp string `json:"timestamp"`
data string `json:"data"`
previousHash string `json:"previousHash"`
hash string `json:"hash"`
nonce int `json:"nonce"`
}
When I try to inspect my structure with:
b, err := json.Marshal(blockchain)
if err != nil {
panic(err)
}
fmt.Println(string(b))
I get:
runtime: goroutine stack exceeds 1000000000-byte limit
fatal error: stack overflow
runtime stack:
runtime.throw(0x4e4094, 0xe)
Also, when initializing
var blockchain = new(Blockchain)
func (blockchain *Blockchain) AddBlock(block Block) []Block {
block.previousHash = latestBlock().hash
blockchain.blocks = append(blockchain.blocks, mineBlock(blockchain.difficulty))
return blockchain.blocks
}
func latestBlock() Block{
return blockchain.blocks[len(blockchain.blocks)-1]
}
When I do:
var s = fmt.Sprintf("%#+v", *blockchain)
print(s)
I get:
main.Blockchain{blocks:[]main.Block{main.Block{index:1, timestamp:"2019-04-06 19:21:37", data:"Genesis block", previousHash:"", hash:"54baff26aa7411352c7879c4ad4bdb86cae07d667d1ed1962225bf0f464f78a0", nonce:0}, main.Block{index:2, timestamp:"2019-04-06 19:21:37", data:"d.duck", previousHash:"54baff26aa7411352c7879c4ad4bdb86cae07d667d1ed1962225bf0f464f78a0", hash:"c4e5d38c907c5b5db77f651880121ebbcb75b1c26d476071d9d69e4ae70e6a11", nonce:1}, main.Block{index:3, timestamp:"2019-04-06 19:21:37", data:"dumbo", previousHash:"c4e5d38c907c5b5db77f651880121ebbcb75b1c26d476071d9d69e4ae70e6a11", hash:"12c3f3595ce28923204c87a6e244ec66c34a7efb13a3acd3b6b57cea75a629d8", nonce:2}, main.Block{index:4, timestamp:"2019-04-06 19:21:37", data:"clown", previousHash:"12c3f3595ce28923204c87a6e244ec66c34a7efb13a3acd3b6b57cea75a629d8", hash:"8907be04c22ed0bc1d7d7b7ce13cf86f11f6fb3261ee34aaafc1fe6a703320b5", nonce:3}, main.Block{index:5, timestamp:"2019-04-06 19:21:37", data:"cod", previousHash:"8907be04c22ed0bc1d7d7b7ce13cf86f11f6fb3261ee34aaafc1fe6a703320b5", hash:"2d514943c6d86940dfca66e720c2aeade7de1fa1a053d36f81cbb134c02d0f26", nonce:4}, main.Block{index:6, timestamp:"2019-04-06 19:21:37", data:"omaha, omaha", previousHash:"2d514943c6d86940dfca66e720c2aeade7de1fa1a053d36f81cbb134c02d0f26", hash:"ef630c9a270a0ac52a2f5a0e2821ea91807b2471e4e4f7204c2edb4f44dd231b", nonce:5}, main.Block{index:7, timestamp:"2019-04-06 19:21:37", data:"double", previousHash:"ef630c9a270a0ac52a2f5a0e2821ea91807b2471e4e4f7204c2edb4f44dd231b", hash:"0c72339be0b54f7e87fcf48adf13f1d3b0e00ba56660906e8283758a74591ca3", nonce:6}, main.Block{index:8, timestamp:"2019-04-06 19:21:37", data:"fake", previousHash:"0c72339be0b54f7e87fcf48adf13f1d3b0e00ba56660906e8283758a74591ca3", hash:"ca31e0372579f0bfb00ac2ddb2127de0dff4d500f7dd6c507db7439380a40862", nonce:7}, main.Block{index:9, timestamp:"2019-04-06 19:21:37", data:"reverse", previousHash:"ca31e0372579f0bfb00ac2ddb2127de0dff4d500f7dd6c507db7439380a40862", hash:"ce4a1386c3aa9e45d1a5d5d3cc5a7d9d0b4e0e2d153a7c9518369a3ee65d5368", nonce:8}}, difficulty:4}
The keys and fields are visible but the keys are not enclosed in double quotes like the values are.
Updated the structs to have exportable fields.
type Blockchain struct{
Blocks []Block `json:"blocks"`
Difficulty int `json:"difficulty"`
}
type Block struct{
Index int `json:"index"`
Timestamp string `json:"timestamp"`
Data string `json:"data"`
PreviousHash string `json:"previousHash"`
Hash string `json:"hash"`
Nonce int `json:"nonce"`
}
When trying the same Marshal again I get the same error.
The program runs out of stack space because the Blockchain.MarshalJSON method and json.Marshal function call each other recursively.
Fix by deleting Blockchain.MarshalJSON method. The method is not needed.